@DarKcapricoRn
Nice illustration. PPTP may be simple, but according to the docs for pfSense 1.2.3, there are a few limitations specific to the implementation of pptp on pfsense that may limit your ability to have more than one concurrent connection to the same pptp server. I've never tried this though, and even if this is a limitation, there is likely a workaround.
But, you may be able to use another method of tunneling traffic. I've used ssh to create tunnels from one location to another. Ssh even supports dynamic SOCKS proxies. If you only want to try to load balance traffic, perhaps you could create two ssh tunnels with socks (look for the -D option) on different ports/ip addresses on your local network which will be connected to the host outside your network. You could configure each ssh client instance to take different routes to the outside host such that each instance would use each of your WAN ISP connections. Then you could loadbalance using the server option. Note: I've never actually used server loadbalancing with pfSense, only gateway loadbalancing.
If there really is a limitation for pptp vpns running on pfSense and you and your tutor want to use pptp, perhaps you could use separate pfsense boxes to maintain the desired vpn connections separately, then use a third instance of pfSense to handle the loadbalancing. I have used pfSense virtualized and it seems to work fine. But I don't deal with heavy traffic.
HTH,
-Joshua
