Thats a total of approx 980 most of which I should be able to get back when/if selling the M4. I have no experience in RF's whatsoever but if I where looking to get into them thats about how Ill do it. If it catches I would get the Leitz lenses.
BTW aren't the CV lenses quite good?
But if one should follow up on your suggestion Id say get some Zeiss glass for the Nikon.