Why a larger fleet does not require giant auxiliaries

Would a no-treaty Royal Navy need much larger Royal Fleet Auxiliary ships?

Not necessarily; merchant shipping and a global base network could carry stores over long routes, leaving fast auxiliaries to bridge the shorter distance from the nearest base to the fleet.

Strategic lift between bases differs from the final delivery of fuel and stores to an operating fleet. Commercial ships can handle much of the first task, while the RFA concentrates on routes without regular traffic and on the fast last leg. Larger auxiliaries demand more power to remain fast, so a no-treaty fleet might need somewhat more ships or modestly larger ones without abandoning the efficiencies of Britain's base network.