Unfortunately, without a strategic system worth bombing the B29s sole target will be hangers at airfields.
Add that to the fact the perk cost will put them above 25k routinely and you might as well have Skuzzy logging in and disabling fields, because neither one is going to add to the game anyway.
One main target will be the same it now is: Towns. Particular town centers, in the quest for highest landed points
Also, climbing to 25K and above will reduce efficiency in a strict sense. You are relatively safe up there, but it takes a lot of time to get there, and you still can't shut down a field on your own in one pass. Of course a few guys can wing up, but that again creates a nice darbar. A single guy can loiter at 25k, he will be a prime target for interceptors during that time. A 109K-4 takes only 7 minutes from sea level to 25K, 9 minutes to 30k.
IMHO, heavy fighter raids are a much bigger threat in this game. A mid size mission in ponies can quickly climb to 15k, dart to an enemy field and shut it down in a few moments. It's almost impossible to intercept them effectively in time. Unlike the buffs they can then take care of any defenders that got up in time.
A completely different thing that comes to my mind: What impact the rain of bombs & explosions might have on lag & framerates. I think of the huge TT missions. 10 pilots in formation with 40x500 lbs bombs loadout... That's 1200 bombs and explosions