I think this is a really cool idea. I do think different types of enemies would benefit if you plan to expand this in the future. I think this game really needs enemies that force you to move, like enemies that deal damage instead of heal, or enemies that shoot bullets themselves. I found that you could shoot yourself into a group of enemies, wait to be healed, dynamite and then repeat, and the game was pretty easy and repetitive because of that. But I do see the possibility of a lot of fun here.