Limey,
"LAN" should be broken up into:
1) Guest wireless network.
2) Internal wired network
3) Apple Server network.
This means we will have a total of seven interfaces when both T-1's are operational and six when we turn off the single T-1.
No, those are all local networks. If you're trusting a router to properly route them only to the WAN and not to each other, then you should trust a router to do the exact same thing one step before plugging into the WAN router.