Yeah so I think that the only thing you could do would be look at average gain with an error band either side (maybe the 95% interval or something to remove wild outliers).
Someone on another thread has built a spreadsheet model of gains from plans based on TR users self-reported data - it just kicks out average (mean) gain for a certain duration plan. This is from a pretty limited dataset but with the amount of data TR has you could obviously do a lot more personalised estimates based on age, volume, plan compliance etc.
As above based on Nate’s Instagram such a feature does exist internally in TR to some extent, but it’s not been released and we can only speculate why (I do a bit of speculation in that linked thread…)