Religious matter/seller equity special structure

I have a weird situation, seller' church restricting the old man to take equity position outside of his religion, given I do not belong to his religion. He wants to structure it in a way that it is not directly equity but acts as an equity with no payouts but has my call option to buy him out within 10 years. Obviously I do not want to give a seller note or convertible note because it still is a debt on books now or in future...what now!

Any suggestions here......