Wow! Really interesting concept! I like the idea that the top side of the dice determines what weapon I can use. The weapon recoil is fun. Shooting a laser and seeing myself get yeeted to the other side never gets old. Melee enemies are the biggest challenge. I often find myself getting cornered by them. They add a new layer of decision-making since they impose a larger threat to players. But getting trapped without a way to fight back can be frustrating.
Maybe 1 or 2 seconds of I-frame after getting hit (changing collision profile to something that ignores enemy collision)? For a physics-based game, this is probably not the best idea. And it will be weird seeing players passing through enemies. Another idea is to change melee enemies to short-ranged ranged enemies (like a shotgunner). Poker cards have a unique bending melee attack. Maybe instead of melee, it generates a gust of wind at its "stomach" that propel players? Adding a longer cooldown to melee attacks may also help. While in cd, the card will stand still instead of moving toward the player.