DOS:
Edgier Fairy-types- I love the idea of a type that can make dragons less OP, but all the fairy-types from Gen 6 have been very cutesy. If they could make a Pokemon based on an evil fairy, that would be awesome. Obviously, its type would be Dark/Fairy. This probably will happen because they wouldn't make all Pokemon of one type similar to each other.
Gyms that we haven't seen in a while: Gyms are a staple of the Pokemon franchise, so it's hard to keep them fresh. Hence, there should be gym types we haven't had for a long time. We haven't had a Psychic type gym since Gen 3. Even though we had a Poison-type gym in Gen 5, it was only in BW2 and it was early in the game. Aside from that, we haven't had a Poison gym since Gen 1! Not counting Chili in BW, we haven't had a fire type since Gen 3. We've only had two Steel gyms and Steel is one of my favorite types. Finally, we haven't had a Dark or Fairy type gym ever! With Fairy, it's obvious why there hasn't been a gym for it yet, but Dark has no excuse.
A new IV system: I don't know what form this would take, but people need to be able to get competitively viable Pokemon without cheating to make sure their Pokemon have the right IVs.
Make all Pokemon usable in-game: By this, I essentially mean no Pokemon that A: Evolve past Level 50 or B: Are in the Regional Pokedex but not available until the postgame. And speaking of the Regional Pokedex...
A Big Regional Pokedex: I didn't like that BW only let you use 5th Gen Pokemon. I think XY should have a really big regional Pokedex with useful Pokemon from all generations.
DON'TS:
A Fire/Fighting Fennekin Evolution: Just no. On the plus side, it probably won't happen because the same guy who leaked the Fairy type, Inkay/Malimar, Pangoro, and a lot more stuff that ended up being true leaked this:
An easy E4: I want a really challenging Elite 4, especially with the Champion. I definitely think that the Champion should use multiple types and that he/she should be incredibly hard, harder than BW/BW2.
Sylveon is the only new evolution of an old Pokemon: It seems weird that they would do this, but it almost seems like it will happen only because none of these Corocoro leaks have shown any new evolutions other than Sylveon. We probably will get more new evolutions, though.
What do you think of my Dos and Don'ts?