As far as what Capcom can REALISTICALLY make a DMC5 game and still would make me happy would include the following:
*Updated combat system from DMC4. Nero has a few more weapons and Dante has a few more weapons/abilities that he can change from his current set up. I would be perfectly fine with them replacing Nero with Vergil as well and opting to go for a new system based around Vergil. Please keep hard lock on. It wouldn't be a big leap over DMC4 at all but even small modifications to the DMC4 system is enough at this point. What they need to do is x copy the tips and loading screen stuff from DmC so people have an idea of what they can actually do in the combat system.
*Better enemy AI and designs. I felt like Capcom made a good step with DMC4 but it's not quite where it should be. I want more focus to be put on challenging enemy encounters. I also felt that DmC had some good ideas (and some bad ones) that the Japanese team could learn from.
*Bosses on par with the older DMC series. More humanoid, mid sized bosses with a lot of tools vs giant blob sized enemies with like 4-5 attacks only.
*Updated graphics engine. I want more detail in the environments as compared to the offerings of DMC4 but I want it to run it on 60FPS. With next-gen hardware this is not a difficult request.
*I wouldn't mind if they kept the platforming or improved it but I want a slightly different level design formula than what we are used to now. It's next gen so it should give them an excuse to go for a bigger scope. If they keep the platforming they need to add more gimmicks to it or just make it take up less of the game because there is a shit ton of platforming in DmC that I just didn't care for.
*This is probably the hardest request IMO but I want a decent story for once with good characters. No I don't want Lady/Trish shoehorned in just for fan service purposes. I want Dante to act his age sometimes in the game and I want him to be mentally/physically challenged for once. All in all if it has Vergil, SWAG AS FUCK cutscenes and the story isn't garbage, I would probably be OK with it.
*They need to add at least one new feature to DMC that pushes the genre forward. I have a few ideas for it but I want Capcom to surprise me. A new mode like Bloody Palace, a customizable arena, a multiplayer mode.. anything new that they can supplement the campaign with. Aside from this feature they better not skimp on any other feature meaning I want BP, Turbo mode, more costumes, all difficulty modes etc.
*NO backtracking, mission retreads or boss repeats (unless the boss is a big part of the story AND greatly changes from each encounter like Vergil) or Dice/Gyro puzzles or Swimming/Flying missions. Please I don't want to see this shit in a DMC game again. DMC4 would've been an excellent action game were it not for some of these factors and it's one of the main reason I feel the old series deserves another chance to provide a more focused experience.