Considering towards the end of Beast Wars they did this with the Unproduced beast to beast figures and got The Mutants, it's not like it hasn't happened before. I mean all you need to do is essentialy give them new heads, their beast modes are fine(abit better than some recent ones like Universe Cheetor). They could also be used to give some real nitche characters a beast era mode or even their first mass produced toy alltogether. Some also would just work better as robots, take the Tri-Rex combiner as an example. It has ones of the best Dinosaur beast modes of any transformer, however the seperate human modes for it just don't work because none of the members even look remotely human.