(straight from email)
• We’re adding a term to make sure our customers use equipment that complies with relevant standards.
• We are adding a right to slow your service if we reasonably believe you’ve breached our Acceptable Use Policy.
• We’re adding more definitions to what we consider ‘unfair, unreasonable or inappropriate use’.
• If a customer treats our people in an abusive or threatening way, we may end the interaction and – in extreme cases – we may stop offering our service to them altogether.
I take the change to mean “no phone support for” not “you can’t use”.
From a hardware point if view; how would they even know you’d changed the firmware?
They probably wouldn’t but it’s the principle of it. But yeah on your first point, it’s certainly a “devil is in the details” type situation. It could range anywhere from “no phone support” to you have to buy and use their bundled modem/router (and everything in between).