I like the concept! I think forcing the player to choose where to place obstacles is very interesting.
Currently, there does seem to be a couple glitches and unintended - I think - happenings. I could cheese the enemy's mine by falling off the platform and then quickly spawning it in, and placing the player's bomb against the ball can cause the ball to fall forward before being blown up.
But, if you were given more time and added more levels and polish, I'd certainly play it!