SNKP should see what Arc System Works did with BB CS and based the game around them (except the online matchmaking)
2 types of challenges, BB style (with 10 challenges for character where you learn combos from basics to advanced) and KOF style (showing some mechanics of the game, even though better explained than in 98UM or 2002UM, and some silly yet funny challenges like the ones in 2002UM)
The training mode in blazblue continuum shift is perfect, has everything
SSF IV arcade style will be a good idea too
Some tutorial for begginers like the one used by Dandy J, or like blazblue will be good too
If they add more characters, I want to see them balancing the game, and hopefully, than an arcade upgrade will be available for them too
Color edit will be cool, but like rex dart said, they should make it a little restringed. Alternate customes is something that I would never hope to happen (there was a big effort with the ones present in KOF XIII, even though all of them are headswaps, it will be a much different story if they tried to change the clothes for everyone)
New stages will be cool too, even though I hope that those new stages are on 2D and not on 3D.
And that's all, even though with a good netcode and some balancing I will not had any problem