You must take into account that any such 'stretching' will affect
production, so unless a marked increase in performance is attained the
stretch isn't going to happen. Wartime priorities all involve time,
and losing production for a minor advantage isn't going to happen. The
stretch to the 190D was because of the drastic engine change,
involving more length and weight up front countered by a longer aft
fuselage. The long wing on the TA152 was for high altitude work; the
original BMW-190 couldn;t get up there and the 109G/K could but wasn't
good enough by 44. BTW The B50 started out as the B54. Why the change
I don't know, unless it was appropriation bills, playing games with
which which changed some other designations (whence the F86D, formerly
the XF95, ISTR).
Walt BJ