How to make "transparent" firewall?

[stramato]

I give up on trying to make Multi-WAN/Load-Balance/Failover + Squid + Port Forwards to work in a single pfSense box.

I think I'll make this setup work easier:
                                                                      gigaLAN
ISP 1 (leased-line 8Mbit) –---[pfSense Multi-WAN]–---------[pfSense Squid + Port Forwarder] –---- users
ISP 2 (adsl 5/0.5) -----------                                                                                        ------ web servers

Is it possible to make the Multi-WAN pfSense firewall "transparent?" So when I configure the "inner" port forwarder, I don't have to configure the "outer" port forwarder?

Also, where would you think it would be practical to put the Traffic Shaper (for blocking torrents primarily and limiting bandwidth per user)

[tacfit]

I believe using 1-1 NAT mappings on the external one should accomplish this. Map each of the external IPs to a virtual IP (of your choosing) on the segment between the two firewalls (the inner firewall would be listening on these virtual IPs). Then create firewalls rules on the outer one that passes all traffic directed to/from those IPs.

Since your lines are of different sizes, you'll need to put the shaper on the external firewall to make much sense.