If there is one thing I wish for in Arma 4 is a new engine. I've played Bohemia games since Operation Flashpoint Cold War Crisis when I was like 8 years old. Although I've always loved the gameplay of OPF/Arma being a huge, amazing sandbox simulator there is that clanky, really weird experience that has always been there. When you are on top of that tiny tower in Takistan for example, you twist 180 degrees and your body is not staying on the same spot when you turn, noo noo, you turn in a very weird way and your hitbox or whatever move in some weird way instead of simply rotating when you turn so you end up falling off the tower. Or that very common experience when you are indoors and everything from your legs to the tip of the gun block so many maneuvers you should be able to do. And all the other stuff that have been there I think it's time to remake it and make it more smooth.
But other than that I want a better AI and more additions to AI behavior, more additions/remake to gameplay like stealth and more interactions. Some additions or remake on how to command the AI, it would be good to have stuff like what type of target they should prioritize, look at two different directions, follow someone, search the buildings in a zone you can make on the map etc.