I think it'd be an interesting idea and it would hearken back to what Hasbro had originally intended for Pretenders to be back in 1988. IDW's Carnivac is a good example of this. Even Bayformers gave us something like this with Alice (although the completely kibble-free robot mode was utter rubbish). I wouldn't mind seeing G1 Pretender characters revisited where they actually transform into their Pretender shells as alt modes. The Pretender Beasts would probably be the most marketable ones to start off with, because they'd essentially be BW TFs with G1 robot modes (like Carnivac). The more adventurous options would be other Pretenders. Would people want to buy robots that transform into humans or monsters? Of course we would, but would the general market be able to absorb it? I'm just not sure if it's commercially viable.

The Pretender Beasts should be doable though - if toys like Generations Waspinator, Rhinox and BW MPs can sell, then I see no reason why a Generations Carnivac, Catilla, Chainclaw or Snarler wouldn't sell. Also, their original alt modes were just robotic versions of their outer shells. Doing non-Pretender Beasts as modern toys might be trickier because what about their original alt modes? e.g. Generations Cloudburst might transform from robot to Femaxian-Queen attracting human, but what about his jet mode? Bludgeon may transform from a robot to patriotically Dutch samurai Skeletor, but what about his tank mode? Previous modern toy versions of Pretenders have just focused on a vehicular alt mode with the robot mode being inspired by the Pretender shell or original robot mode, but never both. Movieverse Bludgeon is a good example of this - the first toy, a redeco of Wreckage, was a homage to Bludgeon's G1 robot mode. The Pretender shell form was completely ignored. The Revenge of the Fallen figure had a tank mode inspired by Bludgeon's G1 alt mode, but the robot mode was purely based on the Pretender shell. The original robot mode was completely ignored. BotCon 2015's Oilmaster's robots are redecos of Generations Swerve and Flanker with a new Pretender shell - the robots do not transform into the shell.

What I'm saying is that we've never seen a G1 Pretender inspired contemporary Transformer that could triple-change between robot, alt mode and shell. I don't know if this is even possible, at least not without invariably compromising the toy's design/engineering. The closest we got was arguably Thunderwing (and thus by extension Black Shadow) - the robot was based on the shell which could transform into the shell's alt mode, but it also came with a detachable drone which resembled the original robot's alt mode (but doesn't transform into a small robot).