The advantage for me of separating the unspent outputs from the transactions is that the transactions are much larger in size (in this scheme) than the unspent outputs, so there is a considerable saving.
Well there are no unspent outputs in the MBC scheme which is why I think your scheme is closer to Bitcoin. If I were to send 1000 micro-transactions to the same address using Cryptonite the account tree would only grow larger on the first transaction, but if the address was already in the account tree before I sent the first tx then the tree wouldn't grow at all. In your scheme the tree would grow for each of those 1000 transactions because you're recording unspent outputs rather than a balance sheet like Cryptonite.
Yes, I was talking about the advantage relative to Bitcoin. I know the account tree in my scheme will be at least an order of magnitude bigger than in the MBC, probably more. I tried to maintain the accounts in the scheme, but it was simply not possible to have a high degree of privacy with reusable accounts.