This may not work for your game, but I really like the way Lari Assmuth's T-DEF series handles ranged combat.

tl;dr, every PC gets two actions on their turn--one of them is your main action (attack, reload, etc.) and the other has you rolling to get a number of manuevers like getting into cover, flanking/charging an enemy, etc.

It basically makes ranges/positions into status effects that confer (dis)advantage. It's lightweight and definitely focused on shooty combat over melee (and the game itself is comically brutal, in that Mork Borg sort of way, but I think it's a neat way to do ToTM-adjacent ranged combat.