Yeah as SonicGuest mentioned, DMZPlus is what you want to look at for bridging.
The DMZPlus device will get a public (WAN) IP address and virtually all traffic will be passed through without any firewalling.
For all intents and purposes, this is "bridge" mode on UVerse routers. You'll be able to do all the port forwarding, firewalling, and whatever else you want from your DMZPlus device and still be able to max out your FTTN speeds with no performance penalty.
Even on non-Sonic ATT UVerse services this is the closest you'll get to bridge mode.