My post is more about whether it would be easier for the dev's and companies to build them separately (but cooperatively) and would it be a viable split in terms of a selling point in the market I guess?
I don't really think it's workable in practice. MP needs a fairly large player base to get to viability. Good-- or rather, adequate -- SP gives a prospective MP player some assurance that he'll have that. Also, branding's an issue. There aren't too many MP games that don't piggyback on some kind of SP to get launched. Having said that, it should be theoretically possible since some games have managed the trick.
Note that it's not at all clear that disaggregation would help SP. MP for both DAI and ME3 struck me as being relatively cheap and highly profitable. Separate the MP budget and revenue from DAI-SP, and does the SP budget stay the same? Or does it drop to match lower projected revenue? I've worked in subscription businesses where our support pricing was, bluntly, exploitative. However, without the exploitative support pricing we wouldn't have done the base products in the first place, since on their own they couldn't be profitable enough.
Maybe we SP players should be cheering on those poor chumps buying the MP chests.