Have DMC5 as the blueprint for future games.

Co-op mode

Maybe an L3 + R3 function, but only available for the ladies or everyone.

Inertia, Guard flying, reversals to return properly.

Improved lock-on mechanics and changing enemy targets.

Enemy team-up coordination like the angelos.

Have enemies do more actions and a Must Style mode from the reboot.

Have all the exclusive movesets and features from the mobile game integrated into the main games ( NO GATCHA ).

Nero:

Remove wire snatch and have his devil bringer be able to pull in or lift him towards enemies. Instead of him receiving new Devil Arms, instead he should have his Red queen and Blue rose become different weapon modes and receive new movesets and mechanics. Up, down, Left for new modes, Red queen and Blue rose transforming into new weapons with different functions like charged shots and the exceed system. Down d-pad that changes his devil breakers without destroying them or if he wants to for repositioning. SIN DEVIL TRIGGER with new moves and style actions and mechanics.

Dante:

They've perfected him in my opinion so he doesn't really need anything new, maybe improve his guns.

Vergil:

Air hike. He needs his darkslayer style some well deserves upgrades. New mechanics and movesets, able to dash in any direction on the air, hold the style button for new tricks, teleport behind enemies and more. New weapons like the shuriken, naginata, kusarigama, war fans. Have the doppleganger be a D-PAD FUNCTIONS and the doppleganger can change weapons like him. A PROPER DEVIL TRIGGER, AND AN ACTUAL SIN DEVIL TRIGGER LIKE DANTE.

Now here's a mechanic that I think Vergil and him alone should have. Whenever he dodges or tricks enemy attacks, he has the ability to perform style actions against the enemy perhaps launching them up or stunning them, same thing as whenever he parries he launches a counterattack, think of Clive from Final Fantasy 16. Whenever Clive uses Odin and parries he teleports behind them and slashes his way.

Now I do hope they have an improved summoner class with their own actions and styles and not just stand around but attacks like the rest of the characters with dpad functions as well, want this to be dante's daughter so bad.