Just gonna say, I would doubt MM Classic getting in due to the reason they did not consider him when they started work on the cast (too bland, and a lack of good melee moves that could be given to him while keeping him faithful to the source material), and X would face similar problems (lets face it, aside from the dashing and armour, he is pretty much MM classic in a new coat of paint). The most unique thing I can think of giving X would be an armour change mechanic, in which he would switch between the different armour's he had in X4/X5/X6, but the problem with that is that the differences between the armours are actually very minimal. I could see him making it in based on fan demand alone, but not so much from a gameplay standpoint.
Also, they did not redesign Jill. They made RE5 Jill. One of the big things they have been striving for with the cast is keeping them as close to the source material as possible, and the new Jill is pretty close to her RE5 incarnation, while still maintaining the over the top nature of the game.