I cannot see any particular gameplay reasons why the B-29 ought not to be added, under certain conditions. As has been suggested, it should be perked, and I really like the idea that it should only take off from the untakable bases surrounding an HQ. Bombload is fine, etc. If someone wants to up a set of B-29s, risking 400-600 perkies, and fly a couple hundred miles to bomb some base, taking a good hour or two for the sortie, then more power to them. There's no really good gameplay reason why they ought not to be able to do so.
But the nuke is out. Sure, would be cool, give it a perk price of 3000 bomber perks so it doesn't get used that often, but it will almost certainly never happen, and is really a different topic altogether. The B-29 was used to drop nukes in WWII two times, but it was used in thousands of sorties to bomb cities and strats and whatnot.
And the God/Kitten joke was funny the first time. That ship has long since sailed. So give it up, please, for all our sakes.
The B-29, without nuke, is a perfectly reasonable request to make for the game, and I cannot see any reasonable gameplay reason it ought not to be there, with suitable perk price and perhaps base restrictions.