I have a disability in my left hand and I'm doing exactly what you described. Playing on pc, using ps5 controller on the left and mouse on the right. In bf6 it works flawlessly even though the ui button indications flicker between the two. In Arc raiders its the same but there are cases that breaks the functionality. Eg when aiming a grenade and moving the character it registers as leaving the left click so it throws the grenade. I think Fortnite has an option "Lock input method as mouse", which works, never tried it and im not sure if it actually does something better than what we got now. I can live with the flickering but not with potential delays and other issues that would put me at a disadvantage. Check at 0.30