I like the idea, so please don't take this the wrong way, I just want to throw this point out there.
If you're Lv6 SS, sell your crossbow at the end of the frist round, then buy your LAR/M14. You don't even need the bow in round one, you should be capable of defending yourself from clots and crawlers with the 9mm especially since you're Lv6.
If you start in later waves, crossbow the scrakes, FP's, and clot clusters, pistol the lesser mobs.
It's always worked for me but I do think that this is a great idea.