let me try to reexplain may idea for the random weapon stuff:
under the weapon setup tab you can select 2 random styles, one is random ones: the weapon stays the one that was picked at start. the other is random repeat: every time you pick up the weapon it gets replaced by a new weapon when respawning...
to limit the selection of weapons the random code can check what you set that out of stuff that now limit the weapon selection menu so that you can say that for the redeemer you want "random repeat out of all overkills" while the chaingun gets "random ones out of all U4E weapons".
now to make the players able to find ammo for these weapons one can have to choises under the ammo tab, one that says match ammo to gun so that the ammo matches the gun replacing lets say the pulse rifle, this may not with the random repeat setting for the pulserifle tho unless the that ammo changes every time the pulse rifle replacement reapears...
one other thing that can be put under ammo is a generic ammo crate or something similar (it may be there allready tho, i cant say i have looked that hard) that fills every weapon you have with the same amount of ammo, this may make the overkill weapons way to easy to find ammo for tho...