I think the B-25C is the fastest of the Mitchels and still able to outrun 109E-4s. It even has WEP. It soaks up gobs of cannon rounds with no damage. Had this come up in Aleutians campain a while back in FSO. A6M2s had a hard time closing with the B-25Cs (formations disabled) and I even managed to unload my entire cannon compliment into a single B-25B with limited damage. I then unloaded well over 1000 7mm rounds on an un-moving target (he was fixated on my carrier below!) from 600 to 400 yards out and never did any damage. They were all in the same spot, in the wing root and engine of the left wing, and never brought it down.
B-25Cs are lovely planes, don't get me wrong. They just don't belong as-is in early war scenarios. They're modeled out of steel.
I'd love to see a Blenheim. Old, slow, weak, sure. But they saw use and would be a good light bomber for early early war scenarios. (his, of course, in addition to the Better, the Heinkel, and others.)