Hi.
I have a pretty short list, but it is something I would REALLY love to see in the game.
I have always wanted the game to be playable in 64-bit (Which they are implementing now). Thanks Bohemia!
Another performance based suggestion I have is adding Vulcan support. Not sure if they are already busy with that, but I think it would make an excellent improvement on the game's performance. I know it may be a lot of work, I just hope BI would use it in their future Arma games at least then.
The last one I want and this is my biggest wish for Arma 3 and any future Arma game. That is more more more more CTI scenarios!
I freaking love the CTI scenarios and I was really disappointed when I couldn't find any in Arma 3. I know there are mods like the BeCTI mod, but Bohemia made the best CTI scenarios in Arma 2. It would be a dream come true if Bohemia made some CTI scenarios again.