Pinsir.
Pinsir should become a Bug Dragon, Pinsnap, or something. I think that would be cool. Only evolves when holding the Dragon scale, in the Dragon's den. (area in gen 5, they should make. lol)
If Tauros got a Pre evo, it would have to also be one that could evolve into Miltank, as those 2 are the same species. When you breed for either, you have a 50/50 chance of the egg being w/e. So, a pre evo, would need to be like genderless or something.
I already said about shuckle in my other post here. But Quilfish, was pretty cool, they should give him an prevo and and evo. Quilby, and Sporfisk. lol.