It was a good idea, desinged to bomb targets in the US, but it was just one of those great things thought up in WW2 that never made it, however, they did have tanker submarines, which were use to refuel float planes on there way to bombing pearl harbour, so, in a compromise, once we even get opperational subs in AH, as well as floatplanes ie H8K2 there could be room for TG like subs that you could refuel from at sea, you have lots of unique ideas, and with a little refinement and a bit more research, I foresee that you will start to put out some unique ideas that no one has thought of before