The B-25s on the Doolittle raid only carried 4 x 500lbs bombs - you can put that loadout onto an Avenger now and get the same results. It'd be fun to try a taking a B-25 off a carrier now and again, but if I needed to get something at a base wacked, I think I'd be taking an F6F with 2 x 1000lb bombs and load of rockets.
That said - I still am in favor of having the B-25, various types and loadouts available. The 75mm anti-shipping variant would be interesting to try, and would eliminate the "bomber zapper" argument that is so prevalent in other threads discussing large caliber guns on Me-410s, Mossies, etc.
EagleDNY