Difficult to put my thoughts on this one when Aeron basically already has. Like, to a tee. The story's great but the execution leaves me wanting more--I lost at Wave 20 because I ran into a presumably-shotgun enemy that was completely off-screen in an edge I hadn't explored yet. It jumps from pretty easy to being jumped by the actual mafia once you're down 40 enemies or so. It'd also be nice to have a weapon guarantee a drop the first time you see it, since the other half of why I died was being unfamiliar with the tommy gun needing to cool down as it didn't drop the previous 3 times. :P
If you develop this or even this idea any further, I'd love to see it! In any case I will happily keep tabs on wherever you go from here :)