Ah yikes yeah I can imagine that's rough, hahah. My game also has all of the level design be done through code, but since it's only two dimensions it's a lot easier to imagine and visualize and since it's purely "wave based" I can simply set a timer to spawn at any wave any time I want. But for this kind of game I think it'd be better if you were actually travelling through a real location with the enemies actually placed where they would be (besides spawners of course). I'm not too knowledgeable on 3D game development in general though so I don't know what would be most "optimal" but it sounds like it'd be something like that. As for the weapon stability thing, simply having more enemies that try to "get in your way" and improving the aiming would do a lot. You could have boss fights where enemies spawn periodically and you have to sort of "pick" in the moment which weapon you like best for that boss or something. Just throwing stuff out there- I think you're on the right track either way.