This is all in my mind and not down yet on paper. How about doing a subject to deal with options and leases.
You do a lease with an option to buy. The now home owner gives you an option to buy. The term is on or before the amortization of the mortgage termination. The strike price is the loan balance. You have a master lease with the right to sublet running the same concurrent term. Of course you protect your interest with documents in escrow. You have a mortgage of option recorded. You are named additionally insured on insurance. POA to deal with escrow and insurance. Of course you control the payment on the first position debt with a letter of instruction to accept payments of such.
That works. Economics would tie out the same, you just won’t get the deed. I personally hate sub2’s given the amount of service providers in a transaction that don’t understand it and will try and kill your deal. Just be sure to put provisions in place that when you want to close on next transaction, seller involvement is minimal/none.