Generally, I've no qualms with MS per se but this is something where the reward isn't worth the risk. Card issuers really frown on this, in particular Amex, any suspicion you may be circumventing cash advance fees would lead to your accounts being closed. The worst case scenario is that if you were unlucky enough to get caught up in any kind of money laundering investigation. It's not worth it, in my view.
As I'm sure you well know, when running a business it's of vital importance to not only avoid any violation of State or Fed laws, but also to stay clear of even the mere appearance of impropriety.