Interesting about the inflatable, that makes things more plausible from a crew habitability standpoint.We already know BEAM will fit in a Dragon Trunk, so if they used Dragon, then they could in theory deploy BEAM out the back of the Trunk, then flip the Dragon around 180 degrees and dock to the BEAM (obviously BEAM would need a compatible docking port, as the ISS CBM couldn't be used). Plus such a proposal would only require one launch.
A sidenote, but I really wish I knew more about that reactor on ISS.