You are not your end users. I’ve had services terminated because script kiddies attacked me. Literally nothing in my control, it was bad optics for the provider (and their customers). So you must find a way to insulate yourself. Multiple accounts is the way.

Think of it like this, when you are doing your accounting you don’t put everything on a single line item, you separate by customer to understand where your profit and losses are occurring. Same with service accounts

At a certain size, your org should be a resale partner with whatever cloud service it is, so the end customers are getting their own accounts. This varies by size and $$$ spent.

Credit cards should never be linked across accounts thanks to PCI-DSS complince

Same IP ban is also not likely unless you are actually doing nefarious things across multiple accounts. I am also making the assumption you are connecting from some business account and not a residential ISP, though that is changing thanks to covid. FWIW, I have worked at many companies where offices of 300-500 proxy outbound traffic to a single IP, that’s why I don’t believe this is a concern.

The ultimate problem is when you have several logical partition but no billing partition. Also the large marketing firm I worked at had zero phone support with Facebook and Google, yet we did this all day (with a single IP address).

This all boils down to one common thread: you should be taking advice from a lawyer on whether the terms prevent such actions and to have a business continuity plan. If the vendor does something egregious, like shutdown all accounts, then your lawyer can ship them a nice letter which will get their attention