Greg, don't get me wrong - I'm not criticizing Martin for a non-installation of a power-opearted turret (whether remotely- or 'directly-' controled) in the early days of the B-26.
Had the costumer (USAAC) been more modest (realistic?) with some requirements, esp. re. crew size/accomodation, had Martin/Marguder installed better Flap system, had the best possible R-2800 got installed, had the, now USAAF managed to restrain themselves from again upping the capability (= weight) - then yes, we'd see the B-26 making 350 mph by 1943. But too many 'if they only did this is' are involved, and B-26 historically went to the ever increasing weight & drag spiral, with engine power increased just a bit, and result was the slow bomber for standards of 1943 and later.
BTW - looking here, the wings were not that thick on the early B-26 - 16.7% at root.
The A-26 was ordered as an attack aircraft, that probably kept the crew size low, and indeed it used newer aerodynamics and other technological advances to it's advantage. The only 'legacy', or low hech items in 1944 were the engines, single stage supercharged R-2800s, B series, in production from late 1941/early 1942.
But how did the B-26 compare to its competitors (B-25)?