Zwift…move to points/ranking versus power and weight based. Allow for promotion AND demotion based on the points. You race a lot and learn to do well with the power you have and win a lot, you move up. You lose some power and start always getting dropped, you lose points and get demoted.
I think that’s more susceptible to gaming than W/kg. Train for a few months in races, being sure to just dangle off the back during every finish. Get demoted. Once the ZRL season rolls around, you’re in prime sandbagging form. Just finish in the top 3-4 most of the season to avoid making yourself too obvious, then dominate the last race.
If there’s a perfect solution to sandbagging (other than people being…good people and unlike jaretj), I don’t know what it is.