I would think I'd rather avoid the whole issue via nerfing hitscan and high-velocity-projectile weapons, and buffing lower-velocity-projectile and melee weapons

I would think I'd rather avoid the whole issue via nerfing hitscan and high-velocity-projectile weapons, and buffing lower-velocity-projectile and melee weapons. There have been successful FPS games with that formula (Tribes comes to mind). There are cheats/hacked clients, but they're on a much less problematic level (mostly around visibility).