By telling the person who doesn't want to opt in "too bad, your checks and ACH transactions will bounce now, too" - you are conditioning the opt-in. You are subjecting the person who didn't opt in to additional hardship (or at least that's how it would be looked at) - bouncing a check will mean that they get assessed fees by you PLUS fees from the payee.
Basically, one group of people will have coverage for checks and ACH, the other group will not. It's definitely in violation of the reg.
We were also told our systems couldn't accomodate that. Guess what - after several months of work, they can. Shocking...
And we're ready to go early next month.