rebelais: Glad you're having fun with it! Your questions ->
>what is "potential"? is it mirrored in intangibles, or entirely hidden?
Potential is a hidden stat all to itself that measures how well a warrior may develop, given the proper environment and luck on your side. It can range from 8 or 10 all the way to 180 or 190 (on a 1-200 scale). Of course, not knowing this number makes the player have to use their own judgment when evaluating warriors. Things like injuries, illnesses and bad luck may keep them from developing to their full potential (similar to real life sports) as well.
>Does using magic incur any kind of danger/penalty/loss of warrior potential assuming you aren't caught?
Not really, but if you are caught (very rare), the fines can be huge. Also, spells can cost quite a bit of money and the more powerful ones usually have very random effectiveness and other costs, so they're not a sure thing.
>Is there any benefit to winning (on a team level) other than financial? My manager stats didn't move a bit during the 18-2 year even with max advertising/training in the Last 15 bouts.
I have added more chances for the manager stats to move up or down in the full Version. Winning can improve your repuatation occasionally as well, which in turn can make warriors generally easier to sign to contracts, while a heavy losing rep can make some warriors harder to sign (i.e. In baseball, players would rather play for the Brewers than the Yankees).
>is maxing training most effective, assuming one has the cash?
Sometimes, but not always. You'll have to watch your players to see if they're developing enough to warrant the cost, or you may end up throwing a lot of money away.
Also a note on your intended "use the scrubs while training your better warriors", this is a viable tactic in the game, but...a losing manager may have a little bit of a harder time resigning their warriors later on, so this might backfire on you a bit, and attendance may go down a bit (the people say, "oh, there's that rebelais and his bunch of loser fighters, why go see them today?", which may result in lower revenue overall in the long run. A word of warning.
Thank you for your intended pre-order, and I hope you have fun!