Yes, the Betty would have little use in the MA (but the 20mm defensive guns would be pretty funny). But with the impending arrival of the ToD, I suspect that plane development will be focused on fleshing out specific Planesets that can be used in that concept.
Certainly, planes that fullfill uses both in the ToD, and in the MA exist (the Ki-84 being a prime example). As it stands, I don't feel the B-29 would work in the ToD, as there isn't anything modeled that could intercept the thing.
I agree that one of the Tupolevs would be handy though.
-Sik