Here's a few suggestions to make the combat more engaging:
- add a front-facing pose when you are aiming up, rotating the arms and upper body
- hitting a melee-immune ennemies with a melee attack could stun/push them
- firing the gun could give a small amount of exp, a consolation prize when you waste a shot
If you intend for the sex to be mandatory it could be used in a few ways:
- eggs could be throwable items that distract enemies
- changing the gun to be an experimental biotech weapon would open the door to you gestating various ammo types
- some puzzles could require you to bait an enemy to a specific spot or birth a specific offspring