I think the Boston III should have rocket capability and the A20 not.  However, the A20 should keep its 8 bombs capability and the A20 should not.  The other thing is regarding that drop tank- with the Boston loaded with %100 fuel it only has roughly 30 min of flight, I would for sure use that DT if given the chance.  I'd fly a whole lot more bomber missions in Bostons if I could get further.  At 12,000, the Boston moves right along at 340mph TAS.