Not a bad idea. There are quite a few characters that I'd prefer never get into Smash as playable, but I'll narrow it down to 10. This is all my opinion. Lower the pitchforks.
1. Dante - All the reasons that you listed. The best incarnation of a playable Dante already exists in MvC 3. Smash won't blow my mind any further than MvC did with his move set. Guaranteed.
2. 2B - Or not 2B... That is the question.. Having played Nier Automata, I can see why her being in Smash would cross some minds. Playable though? No thanks. I did not care for the story at all and its not like she would bring anything "completely unique" to the table. I realize that we are lacking in female DLC, but that can easily go to more iconic characters like Lara Croft, Shantae, Dixie Kong, etc. I would've loved to have Ms. Pac-man.
3. A new Pokemon - I just don't want anymore Pokemon unless they are from Gen 1, which won't happen.
4. Amaterasu - Same reason as Dante.
.That's all I have to say. Have a nice day!