Revamp the whole system and do this:
Instead of brewing 10 or 20 gallons at a time, get a 7-bbl system, and get your number of customers lined up for the next batch. At pitching time, you will need to split up the pitch between the the max number of gallons of beer per year that a homebrewer can make so that if you have a request for say 200 gallons and that the max per year a homebrewer can do is 200 gallons, you only need one customer to pitch the yeast. Of course at that point, he's done for the number of pitches that he can do for the year. This would have to be calculated/accounted for properly.
Then the next time, another customer can pitch the yeast but the same (previous) pitching customers can still chip in and buy some, they're just not pitching the yeast anymore. They'd be limited to the number of gallons purchased per year.
In effect, you'd be allowing a customer to pitch yeast for up to 200 gallons max, and to purchase a max of 200-gallons throughout the year. (this assumes a max per yer of 200 gallons per person).
If your batch size is bigger than 200-gallons, say 275, you'd need 2 yeast pitchers to keep it legal.
This larger batch size would greatly cut down on the number of batches to be done and especially on the number of hours spent brewing overall. Of course you'd need a bottling line.
If you're savvy and technology oriented, you send out "next batch: hefeweizen", and get your orders in, tally them one week before the brew session, and place your grain/hops/yeast order from your supplier(s).
You're essentially removing the legality of having a brewing/liquor license by having the customers pitch the yeast.
I have no idea if it'd fly, but it's a thought.
M_C