I know Reg O focuses on overdraft fees, but is there any problem about waiving a different type of fee, like a sweep
fee, on a deposit account of a business owned by a board member?

Do you waive these fees for other customers? Its only allowable if its a customary practice for all customers.

It looks like we've waived the fee for 2 other customers, but not for all the other customers in this product. And I believe they were talking about waiving this fee ongoing.

So, Reg O does care about fees other than OD fees? Is that supported somewhere in the reg that I'm missing?

The reg only talks to OD fees, but I will still be careful about waiving fees for anyone that falls under Reg O if its not a regular customary practice.

Yep- that's my stance on this too. Better safe than sorry.
Thanks!