Ammo should be shared by all weapons exept the polar star, and enimies don't drop expirience, but still drop health and ammo. Also, could the polar star become a melee weapon?
"exept the polar star"
Then I don't think it's worth the effort. Eh, I might try, but then... Oh well. I have the entire night to try.
And if you don't use levels, that could even be easy (melee wpn)