thank you. wanted to tell you I don't like fps or shooter games so you really made a masterpiece here :)
if you do want to add enemies make them fly and move slowly. making them shoot seems useless unless you give it hacks (maybe no schooting)
a ground enemy woud be cool say you can jump on his head to get a giant boost! its like the bounce blocks but you can only use it once and it attacks you
i hope you like these ideas :)