For those reasons (and others), I don't think your proposed legislation would work.
There are a bunch of people who nobody wants to insure. The government basically divides up those people, and forces insurance companies to take them on as customers, since insurance is legally required in some cases.
In order to make sure these customers don't hurt the main business, the insurance company has a separate legal entity to handle those customers.
In the case of adult entertainment etc, the government’s regulation has cause the risk, and that untouchability, so it can’t then endorse the very interaction it was banning. If it could permit these businesses to use banking, then the solution wouldn’t be necessary in the first place.
This is one in a long string of cases where people cannot operate fully legal business because of the policies of the financial institutions.
- "risks that they wish to avoid" seems merely to be a risk to their reputation "what are people going to say should stuff happen". It's a level of "legitimate" that applies to anything. That one is not illegal because sex work is not a protected class (more or less). Otherwise it would be.
- "They have a legal obligation not to facilitate money laundering and human trafficking". Hmmmm. No. A law against, say, human trafficking cannot make adult businesses illegal. Or if it aims to do that, it needs to name it. These businesses are not illegal. A bank has some obligations to be vigilant against some things - and might demand lots of paperwork and might still often do the wrong thing. But society does not need them to go vigilante and blacklist entire domains of legitimate activity.
And blacklisting / red lining is exactly what laws might try to prevent. Seems that sex work needs to become a protected class. (Never mind that "protected class" is american law, not canadian.)