Multi WAN 3G loadbalancing router on ubuntu server

Hi ! I have a mini-ITX server that is running Ubuntu 10.04. I would like to add some routing functionality on it such that it can act as a multi-WAN loadbalancing router that can support 2G/3G cellular WANs. Specifically I need the following: 1) The server will have four 3G modems connected as WAN. The LAN side will be Wifi. The wireless clients should be able to connect using Wifi, and on the WAN side their traffic should be loadbalanced across the 4 cellular WANs. 2) WAN failover : If one WAN fails, the traffic is automatically router to the other WANs. 3) DynDNS capability 4) VPN support 5) Channel bonding to increase bandwidth