The F-111A would be a nice idea for the SAC, some writings in Wikipedia suggested that the internal weapons bay of the aircraft would be used to carry...Falcons, until it is suggested that they are no use against hard-turning MiGs (at least they stay on until the Six went away). Still, it was meant with some limited air-to-air capacity in mind, although they would find trouble against hard-turning MiGs (not a problem if it is a long-ranged battle). Some proposals would involve shoehorning hardware from either projects (F-12 and F-108) into the F-111 (especially the radar, which was somewhat true to an extent), so it is kind of moot that it can happen.
FB designations would usually refer to a fighter-bomber that become an outright bomber of sorts (usually for a bomber derived from a fighter, much like the FB-111 or the rumoured FB-22, although someone or two can correct me if I got it wrong), although to probably convince the government, a less complex designation could be used (something like what the Super Hornet is to the Hornet in terms of designation), to sell the program.
I would love to see how you work it out (been doing the classical side of things now, instead of modern).