Why is it important to ask the managers if their players are capped are not.
Because this is a regression model, something like y = B1x1+B2x2+... where y is the potential and the xs are the skills. If a player is capped, I know y=the player's potential (plus or minus some fuzz due to sub-levels).
If the player is not capped, I have no idea what y is. It is probably something below the player's potential (if they are not capped), but beyond that, I do not know.
...
What is the highest possible REB (for example) of all the benchwarmer potentials. ...
This is kind of suggesting to just take players off the transfer list. Again, I have the same issue as I described above. Even if it seems certain that they are capped, there is nothing to say that they were not trained beyond their cap. Indeed, it is even impossible to say that they are capped. The only way to know is to have an idea of how training went.
Given a large data pool
I still stand by what I said before. With a large pool of bad data (or data with too many question marks), all you are going to get is a bad model.
Anyhow, no worries. I started to get more data. It may take some time, but I believe I will get there. And the last thing I want to do is take a bad path just to get answers faster.
Run of the Mill Canadian Manager