I don't think we care about whether or not this device can be air droped as a bomb quite yet as much as we care about it working the first time and being built quickly. To that end, I would favor conceptualizing this as less a deploy-able bomb, and more the core parts of a bomb surrounded by a shed full of equipment that, collectively, we expect to successfully explode. We can refine that into a bomb later, and if we need one to actually be used ASAP, we either throw together a gun type device, or we put the next exploding shed on a boat. For taking out an invasion fleet, something configured as a sort of nuclear fireship. For second strike capability (at the risk of significant political and economic backlash), some terribly generic freighter that could smuggle it somewhere at need under a false flag.