At present I am trying to develop a MVP, and discussing with some potential dev/engineers around a sweat equity approach. Thank you!
One fair method is the dynamic equity split by Mike Moyer who may have developed this methodology. Basically, you can assign relate values to different contributors, some may contribute time, money, etc, and that equity is adjusted according to recent contributions, not an agreement set in stone a few years ago.
You can find some more detailed information at his site, www.slicingpie.com.
I've looked at Slicing Pie a few times over the years. It seems like a sound practice and helps guide the communication and expectations. I HAVE NOT APPLIED IT ON A PROJECT YET but continue to consider it.