An idea is an idea. I like it, but I don't think it works in this case.
There's very little strategy involved and I didn't feel like I had fun playing it.
Before I knew it, I won and I had no idea what I did that made that victory possible.
That being said, I do want to see this developed further post-jam! One thing that comes to mind are units that have abilities you can activate or speeding up-slowing down units to get around area of effect towers. Think Lemmings, but abilities are decided ahead the time and you just activate them. Point is: I think the player should be able to control more stuff than just when they spawn and how often.