Theory again: Let's take a couple of steps back

[AtticusFinch]

Your points are reasonable, and I certainly considered them. However, I concluded that the model would still be useful for the following reasons.

First, you are correct that I would have to estimate cEV and then run the model for individual players. In fact, that is exactly what I plan to do. However, your notion that I would actually have data for a player's cEV at the level I'm trying to predict is actually a good thing, as it allows me to fully test the validity of the model. If the model fits the data, or can be adjusted to do so, then it could be used to predict results for other players.

Second, while I agree that relative skill level is a vague concept, I think that cEV per hand is a reasonable proxy for it. Limit players use BB/hour as a proxy for skill regularly. The variance is much higher in a NL setting, of course, but with enough data I think that we could produce cEV/hand estimates that would serve as reasonable proxies for broad skill categories such as fish, average, decent, good, excellent, world-class.

All that remains then is to place a player in one of these broad categories, and consult the model for that cEV value.