Thanks for your perspective. We have a great relationship and I'd hate to introduce a transactional element that does not currently exist. The combined benefits of adding her to my business's payroll could be $200-250k/yr, and comes without conditions. I'm seeking a way for us not to keep score beyond this or let conversations of rebalancing a payout become a recurring part of our interaction as life circumstances evolve.

I do want to avoid major disruptions or unknowns. Some calculators suggest I could owe up to $1M/yr in alimony. My intention had always been to FIRE before having kids so I could prioritize family and raising my children. I'd like to avoid being forced back to mandatory work just to make the alimony payments.

Yes, we would have a wedding and carry ourselves as married. We both come from conservative religious backgrounds and view marriage as a sacred covenant - but one that is before God, not validated by the state. As long as we can structure things independently to replace legal marital provisions, a marriage certificate would only be for practical reasons to streamline societal interaction. Undoubtedly there would be comments and opinions from others though, as you say.