Assuming we're still in 'Bee Country, the existing robot designs for most of the surviving robots (with accordingly updated alt-modes) are fine for now...but in the event that this does indeed pan back out into more movies, I also want to see the robot modes evolve beyond their G1 roots into BB-styled versions of other non-Movie incarnations of those characters.
For example, I want to see the guy who spent most of his own movie looking like this...

...looking more like THIS before it's all over:



And the other guy, the one who currently looks like this...

...I want to see ultimately looking closer to THIS:



Likewise, I would not be averse to having this guy...

...ultimately resembling THIS guy:


...and so on, basically. In other words, tweak the characters we already have as new (at least for 'Bee continuity) ones are added, just to keeps things a little fresher.

 

I actually dig this design and some of the other Armada-era designs. Ultimately, it would depend on whomever the writer of the next film would be and the time period it is set in, to some extent. . .

 

Yaaasss!

I like the versions they were in the Bumblebee movie. Modern G1 designs.

 

Again, operating on the idea there'd be more movies in the 'Bee continuity, and that any robots returning from BB will have essentially the same robot designs (if likely more honed and refined and with Earth-based alts) and that the first follow-up would take place not long after BB again going back to my "BB2: Warrior School" idea (and also going with the idea of using cars whose brands are now property of GM, even if they weren't then):
Ratchet ('88 Chevy CK3500 Ambulance)

Ironhide ('89 Dodge W100 Power Ram 4x4)

Brawn ('87 GMC Jimmy)

Arcee ('59 Cadillac El Dorado - I want more classic-car TFs, dammit, and this is a perfect excuse)

Wheeljack ('88 Pontiac Fiero Formula - obviously I wanted him to still be sporty, and initially I thought about a Trans Am, but a talking, self-driving '80s-model Trans Am might invite a lawsuit from Universal Studios,   so...)

Obviously, Ratchet and Ironhide's alts would invoke their previous Movie counterparts, or even more closely their G1-Bayverse-Mixed Aligned incarnations. There may be a little mass-shifting here and there, but I figure if audiences could accept Shatter and Dropkick being able to Triple-Change into THEIR alts, all's fair.

And as Big Bads go, again going back to my "Warrior School" idea...
Robot Mode (Basically a BBfied version of this):

Alt mode (only slightly larger than Dropkick's, but again, if you could sit through Dropkick's Triple-Changing...)

 

i want Live action TFP designs. Except for Soundwave and Bumblebee, I want 2018 Soundwave and 2018 Bumblebee.

 

I do still wonder with Hasbro having more creative control and with these toys they already released means they have made up their mind on what Ratchet's, Ironhide's, and Soundwave's Vehicle forms will be in the Bumblebee sequel, of course ignoring the robot designs of these toys.

 

Retain the autobots and decepticons look of knightverse. And keep the wild creatures of cybertron like Bay's. Constructicons,Driller,Blackout,Brawl etc for variation. No caricatures or human looking robots.

 

Here's for BB sequel characters. I misunderstood the OP post. Since BB was already set in the late 80s (1987), the sequel should be set in the early 90s. Say, 1990-1994.

Optimus Prime

20ft, he continues using the BB design.

Bumblebee

16ft, still a Camaro, but with a new design that fuses his 2007 and BB ending scene appearances. The door wings will be back.

Ratchet

18ft tall, a SAR vehicle like the Hummer complete with a roof rack and a bullbar. White like G1, but with a Bay car.

Ironhide

18ft tall, he carries Bay/Prime's cannons and turns into a red pickup truck.

Arcee

10ft, she turns into a custom pink and white motorbike. She's very lanky and slim to achieve the 10ft height.

Brawn

13ft. A dark green hatchback. Similar in size to Bee Movie Bumblebee.

Spoiler

For legal purposes I know the car in the photo isn't dark green. I'm just setting an example.

Wheeljack

16ft, he transforms into a Lamborghini Diablo or any kind of 90s poster car. Design wise he resembles G1 more than Que. His colours will be mainly white.

Megatron

35ft, he turns into a tank G2 style. I mean it's the 90s, right? He's an M1 Abrams, same as G2 Megs and the basis of Movie Brawl's tank (a fictional one based on the M1). I want to be zany and make him green. Green tank Megatron, anybody?

Starscream (Seekers)

31ft, he turns into an F-15 and has the same robot layout as Blitzwing. Like Bay-scream, he has real-world military colours to play with the "disguise" aspect of him hiding in a flock of US Army jets and discreetly shooting all of them down.

Shockwave

30ft, alt-mode unknown. He keeps his BB opening design.

Soundwave & Co. (Ravage and Laserbeak)

22ft, blue, and similar to RiD2015 and Cyberverse Soundwave. He turns into an SUV and brings back the DOTM tentacles. Ravage and Laserbeak turn into boombox radios. Why? Because he parties like it's the 90s, baby!

(https://image.shutterstock.com/image-vector/90s-retro-radio-stereo-600w-1181772277.jpg)

I want to try an Animated style approach to scale where Autobots are small and Decepticons are much larger. In this case, the Autobots will retain their BB sizes while Decepticons gain the sizes of their Bayverse predecessors.

 

I could get behind this. But I'd change that Camaro because I despise that car.

 

NICE! I especially like your Arcee. Reminds me of an OC that amazing TF artist Grungewerxshop did, below:

 

I'm gonna do my own alt mode list, Because why the hell not?

Autobots:

Optimus Prime: Obviously the Peterbuilt truck he used in Bumblebee.

Bumblebee: 1967 modded Camaro. (the AOE one.)

Ratchet: 1988 Ford E350 XL Econoline Ambulance.

Ironhide: 1987 GMC Stepside Pickup.

Jazz: 1987 Porsche 959 Komfort coupe.

Wheeljack: Lancia Stratos Turbo.
(and a head with no mouth.)

Arcee: Yamaha FZR600.

Bulkhead: Panhard M3.
(I didn't even know this existed until today.)

Sideswipe: 1980 Lamborghini Countach LP400S.

Warpath: M60 tank.


Decepticons:

Megatron: Cybertronian tank.
(because he hates Earth)

Starscream: F-15
Thundercracker: F-15
Skywarp: F-15


Soundwave: 1980s Peacekeeper

Shockwave: Cybertronian Tank (I guess.)

Lugnut: B-2 stealth bomber

Arachnid: Apache

 

Going back to my "robot mode evolution" idea, and given that I have Arcee as a '59 Cadillac in my BB sequel idea, I suppose 'Bee himself would probably upgrade to a more contemporary Camaro for such a sequel (in this case, a third-gen Z28)...

...and again, thinking of 'Bee going up against the Big M on his own in a "Warrior School"-based story, he'd probably get his ^$$ handed to him and end the movie in a coma and dunked in a CR chamber whipped up by Ratchet and 'Jackie at S7 HQ...which would lead into the third movie (using a BB trilogy to build back to a proper full-ensemble TF movie that leads up to the present day) and THIS:

 

I think whenever making a live action version of any character, the design is extremely important. You want it to look different enough to be unique, while keeping true to the source material so it's still iconic in it's own right. You can either pull straight from the pages, or do something new. You don't want another Deadpool from X-Men Origins: Wolverine.
I think if they kept the realism of the Bayverse designs, while also having the traits and design cues from G1, than we might of struck gold. The Bumblebee movie does this, and it looks amazing. I don't want the characters to be a straight up translation of their G1 designs, they should be different in their own right.

 

they look super cool

 

The new designs should resemble their G1 counterparts, but still be distinct. That was one of the problems with bayformers in general. And god forbid they actually go back to human robots. Hope they never do that again.

But I wouldn’t mind a few Bayformer designed bots.

 

Sorry Alpha Trion you gotta go.

 

I think Ken Christiansen’s work on the first two Transformers games were some of the best Movieverse designs we got, that and the Earth designs in Bumblebee. Intricate and complicated enough to for my tastes, but distinct and simple enough to be recognizable. I’d love to see more of that.

 

Honestly the designs in Bumblebee are pretty damn good. I’d maybe smooth out the faces a bit so that there’s not as many panel lines bc for guys like Cliffjumper it makes reading their emotions pretty difficult but honestly they struck the right balance, they look like G1 but real and just a TINY bit busier.

also, I’m totally okay with robots that have facial hair. Again, they aren’t real, so is it REALLY that big of an issue? Just say they grow carbon fiber strands or whatever if it bothers you that much

 

Sideswipe


Mirage


Jolt


Skids


Mudflap

 

I don’t mind “facial hair” as long as it’s not actually trying to be facial hair. Some ornamental thing that kind of resembles facial hair is fine with me, but I hate the big dangly human-like wire beards.

Also, no Mudflap and Skids, please. I love G1 Skids, so for those awful characters to show up and ruin the name of Skids would really grind my gears. I mean, it already happened, but I would love for it to be undone by having the good Skids show people that Skids isn’t this ghetto caricature thing. I’ve wanted a G1 Bumblebee to show up on the big screen to show people that he hasn’t always been a totally epic jock who doesn’t speak, but it seems like that will never happen, so it would be nice if at least a different misrepresented character could get redemption.