I'm not if want as fast and high octane as Devil May Cry or Bayonetta but something with a more tempered pace like Mass effect, I suppose it boiled down to the weapon and play style

So a simple system, armor and weapon weight tied movement and ability cooldowns.

Pistol(s), SMG, Shotty, AR, Sniper, Grenade/Heavy Weapons skill trees.

then general skill and maybe magic that work like the Soulcore system is in Nioh 2/3 tied to types of ammo to instant reload power or parry

Fleshing this out a bit, it could pull from all the cool gun stuff like from Wanted or Equilibrium.

Akimbo pistols would have Gun Kata or you can curve bullets like the fraternity, Active reload/reload cancel but also all the combat power from Mass Effect like Adrenaline rush or Marksman

In fact bring back all the bosses from each of the games as a big send off, I miss a couple of the bosses from Nioh 1 like Ogress and Hundred eyes

Speaking of guns, I wish Team Ninja would make a third-person co-op shooter Nioh spinoff with a Saika descendant as the lead

Mass Effect (basically Space Wizard Gears of War) mixed with Ninja Gaiden with Nioh's depth

Finally getting Devil's Third right

The hyabusa fight should be like Benkei fight with multiple weapons not just two

Also you should fight William and Hide as a final dual boss fight in DLC

Guns as a weapon or at least some gun techniques like Saika in the first two games

This seems to be already done but I'll probably repeat.

Whole open regions with a unique hut, blacksmith and teahouse you have to find for each region, Twilight mission would be enlarged dark realms that shift around every 24 hours in each zone, and an end point that clears all for each level

Wishlist for Nioh 3 basically ideas from since NGB

Proper water running and levels for that

Unlabored Flawlessness Odachi with a similar mechanism and hidden skill drops

Vigoorian Flail/Nunchucks type weapon like murai's chucks similar conceit but for speed

Special Gaki enemy called ITA

I have my "perfect" build, way stronger than what I had when I finished The Depths, casually smoked lvl 30 with this one

The only holes are one of my cores is missing an Anima Bonus (Paralyzed enemy), which I can still grind for in my scroll, and a missing zero ki damage on one of my accessories.