Remember the Dark Designs episode of Beast Wars where Rhinox was converted into a Predacon? I gotta admit the change of the colors is good. But there's one thing missing..... HIS MUTANT FACE!!!! http://www.bwtf.com/toyreview-images/bw/rhinox/rm6.jpg I wish the creators would use the mutant faces in the show. Same goes for "Possession" with Waspinator if only they used the robot face when possessed by Starscream. http://www.bwtf.com/toyreview-images/bw/waspinator/rm6.jpg
The simple answer is they didn't have the budget to model and rig new faces. Besides, it wouldn't exactly make sense, nor would it thematically have sold 'evil Rhinox' if Rhinox didn't even look like himself. Likewise Waspinator growing a new, not-especially-Starscream-looking head doesn't make a lot of sense. (sure his faction symbols changed, but as Rattrap showed us anyone could do that whenever they wanted)
Of course one wonders if they could have found a use for those mutant faces... had the budget permitted of course. Or would it have just ended up so much fluff?
I never really liked the mutant faces, tbh. Although it may because they were never used in the show.
Who knows, the writers were usually pretty good at writing that stuff into the story. They might've just ended up as battle masks, or they might've fundamentally changed the TF, putting them into some sort of berserk mode, so they could fight better. They might've been something entirely different.
I've always considered them to be battle masks due to the fact that some beast faces resemble masks and its in fiction considering T-Wrecks is a redeco of BW Megatron and in the comic he uses it as a battlemask.
Apparently that was the plan, as shown by the early Mainframe models having the mutant faces over normal faces. (and Tarantulas/Waspinator having normal faces at all) But I think it was deemed unecessary because not everyone would've had them, (like Rattrap and Terrorsaur) and much like Primal's own mouthplate, wouldn't have seen much use since characters would still need to retract them during battle so they could emote and speak.
If that's the case I'm a touch surprised they didn't go with it then. You'd think it would save a bit in production costs if they had an excuse to keep the character's faces static during action heavy scenes. Of course then we wouldn't have some of the funny reaction shots we got.
Except it wasn't about saving costs, it was about telling the best story they could, and having the characters seems as lifelike as possible. They had an excuse to not animate the faces during heavy action, it was called just not animating the faces unless they had to. But much like Primal's own battle mask, they'd only have to undeploy them any time they talked, anyway. Making entirely new head designs is a lot of effort to fix a non-existent problem. Actually the original model designs did have mutant faces. So they did at one point intend to carry that gimmick over even within the altered premise of the show. But again, it was likely scrapped because it ultimately served no purpose.
