My opinion?
It's: DUH!!!!
As if the SOLE purpose of Pokemon was to beat the crap out of each others in Pokemon battles or to serve inside of contests.
Just think about it: Pikachu has thunder powers... electricity is useful, people! Use logic!
Charmanders can breathe fire. Fire is useful, you know! Use logic!
Now one that people frown on but that is very obvious. Miltanks are cows. Milk and meat are good, people!
In short, definitely go with it. I always thought that they didn't shown enough utilities for the Pokemon in the games. Their powers cannot be useful only in offensive ways, after all!
... and since trainers are those who own Pokemon and since they need money to live... well, use logic again.
People are willing to pay for electricity, fire, meat, whatever... you catch, train, and breed creatures who can give people all that. You need money to live and maintain your Pokemon in good health and shape. It's obvious that at least one trainer out there will have a genious flash and figure out that Pokemon can be a source of income outside of the classic "beat trainer, get money" way.
Now... let's add some economic theories in there... and your idea becomes so painfully obvious that it's a miracle that so few people think about it when doing fanfics or at least, when adding Pokemon trainers in their fics.
NOTE: I have the awful feeling of my post being aggressive and flame-like while in truth, I am perfectly agreeing with your idea... but well, anyway. Have a nice day!