@David S. I just did an MLO with similar circumstances, seller didn't want to trigger taxes and she had an amazing fixed rate mortgage for 12 more years that I wanted to leverage.
For my MLO I just had to have my real estate attourney email the lender and ask if they had any issues with me leasing the property (there was a weird clause in the mortgage that she couldn't lease the property to anyone even though it was an apartment).
With an MLO make sure the lease never mentions the option. If they cross reference, it could be considered by the IRS a sale and all taxes come due immediately. Also, both the lease and option have to have seperate non cross referenced consideration. While the deal was 10K at signing, 5K per month, 10K on 1st anniversary the formal payments were 9.5K for ML at signing, 5K per month for lease, 500 at signing for option,10K for option at first anniversary.
And make sure you get right to assign the option part at a minimum. It'd be nice to be able to assign the lease but most sellers want to vet who is running their collateral so they won't go for that. By assigning the option you can still sell it down the road without having to hold it for a year to get capital gains vs income tax treatment.