B29 would be fun, but there would have to be some kind of effective high-altitude flack &&/|| something like the Me163 to balance it. As it is I'm generally unmolested at 35K in a B17; a B29 would go higher than the 17 and carry more than the Lanc; it would be virtually untouchable in the main. Definatly a perk plane, but one I'd be inclined to use.
I'd like to see the B24, personally. Bigger load, but easier to kill. Harder to fly, also, and not as tough as the B17.