Yeah, like this hasn't been done before... but I think I've got a couple of new ideas here...
This is a sort of repeat of my Armada Megatron leg articulation trick, using Cybertron Jetfire's legs. It's pretty obvious actually, but I have to admit it hadn't even occurred to me before
Optimist Prime suggested Tidal Wave could get the same treatment over in my Megatron thread! Thanks dude! You were right!!
So in answer to the big question...
YES, Jetfire's legs can be used for Tidal Wave! In fact, it's actually an EASIER mod than with Armada Megatron! It's almost a straight swap with no cutting involved, but at the last minute I hit a little roadblock.
This is how I did it:
No matter how tempting it is DO NOT use Jetfire's complete crotch assembly. It looks like it will fit like a dream, but at the final stage you'll find that his legs don't squeeze together quite enough to transform to boat mode! Grrrrr. Tidal Wave's crotch actually has a subtle taper that allows the legs to squeeze together tight enough to lock the alt mode... which means you actually have to attach Jetfire's legs to Tidal Wave's crotch.
This is annoying but not impossible. The ridged plugs for Jetfire's legs are just much larger than Tidal Wave's so you have to do a lot of shaving and sanding to eventually get them to fit in so you can screw the crotch plate closed again. This means you have to remove the ratcheting assembly, which can leave his legs without enough tension. That upper body is heavy!
I ended up using hockey tape (how Canadian!) to wrap the leg plugs inside to tighten up the joints there. Your mileage may vary, but hip joints on mine are now pretty strong.
Attaching Jetfire's upper legs to Tidal Wave's lower legs at the knee is really easy. First you remove the black ratchet inserts from Jetfire's lower knees, and they fit almost perfectly on the post for Tidal Wave's old legs. You just need to trim a tiny bit at the base of the post so the upper leg goes on flush, and the lower legs close snugly.
Again, this results in an annoying lack of tension below the knee because the ratcheting is lost with Tidal Wave's purple legs. Again, hockey tape to the rescue! I just wrapped a single layer around the connection post before fitting the leg over it, and now it's real tight. Maybe over time the hockey tape will lose some of it's resistance, but for now it does the job just fine.
Ideally, I might do some cutting behind his kneejoints to allow his knees to do a deeper bend, but it's not really necessary. I find the small range of knee movement this mod adds already dramatically increases his ability to take cool poses.
How about those arm mods?
I couldn't quite figure out what it was that was bothering me about Tidal Wave's arms, and then it hit me... the shoulder attachments are too low, resulting in a slumped posture and arms that look awkward, stiff and disproportionate. This mod helps that, since it raises the shoulder connectors (in both configurations).
The arm mod doesn't really require any cutting. You quite simply remove the green shoulder pylons and switch them. This doesn't really affect the transformation... the large connection ports are now facing outward in boat mode (a bit unsightly) and you'll want to cut off the small pegs that now preventing the pylons/pontoons from lining up flush in boat mode. It's also
possible (untested) that the new inside curve of the pontoons will crowd the head too much in boat mode... not an issue for me because I'm replacing the Tidal Wave head with something much smaller.
So... Broadside?
Yeah... in these pictures, you'll notice that I photoshopped out the green just to give me a better idea what he'll look like after I paint him. Not sure if those areas will go grey, white or red.
The head isn't attached yet. You'll notice the old Tidal Wave head is stuck on there just to prop up the Broadside head. I like the way the old head actually looks sort of like a conning tower from the back, so I may try to find a way to keep that part of it in the vehicle mode.
Not sure which configuration I like better for the arms, but once the shoulder pylons are switched, you can arrange them either way.
And tell me... is Classics Jetfire's helmet not a
dead ringer for Broadside?!
zmog
And the fact that it's a bit smaller just accentuates the massiveness of what a transforming naval fleet should look like! Man, I gotta get started on my Tidal Wave! 
