what do you think about MP-TCP. It sounds like the must-have for a personal firewall.
It loadbalances one TCP-Connection above multiple connections, where they can come and go as they which.
The balancing is done with latency and other measurements, which will saturate the best connection.
I am not that much a TCP guy to describe every feature accurately, the best might be you watch by yourself. Here is a nice GoogleTalk about it: http://www.youtube.com/watch?v=02nBaaIoFWU
I would like to accumulate a lot of small Broadband connection in my rural german hometown as to have a big robust uplink for a local fibre-optic network.