I know this is quite a bit of a delayed response here but I figured I’d post anyways because this topic still seems quite relevant around the net. I’ve been researching broadband bonding recently and it is definitely achievable as I know there are a select few companies that sell products capable of doing such. They require no software (i.e. MLPPP) and the ISP’s need no prior knowledge of this for it to work. I’m sure if you just google search “broadband bonding” you can find the answer you’re looking for.