If it's qn excess thrust issue, than that would weight it even further
into the "Yes, sure the B-1 can do an Immelman" side. Of all the
things the B-47 didn't have, thrust
Remember, the B-47 did their immelmans from high altitude (and entered from a
dive obviously), the Afghanistan Bone would be entering from straight and
level, thus it becomes an excess thrust issue.
Well, fly around the pattern trailing a parachute is one... 
Tobogganing behind an overstressed KC-97 would be another.
Cruising around, fully loaded (albeit a smaller load than a BUFF or Bone) at
40K+ and .90 mach. Doing an immelman at high altitude (not possible for a
BUFF...maybe for a Bone, but not from 30K+).
BUFDRVR
"Stay on the bomb run boys, I'm gonna get those bomb doors open if it harelips
everyone on Bear Creek"