An interesting argument. It could be argued that we revert to pre 1918 status quo and have the air arm as part of the RN/RA. It would certainly save top brass. But what we (the UK) really needs to do is to cut our cloth according to our needs. Do we need our armed forces to protect the UK or to protect an long gone empire or to try to be the World's policeman? If it were the later, yes we need occupying forces. If all we need is defence of this Island, then air power alone is sufficient with obviously some submarine sea power to protect the shipping lanes. We then don't need an army and we don't need a nuclear capability.
But I don't have all the answers because I don't have all the facts. But I doubt if anyone else has either.