I ran into this problem with hardware from Soekris, a nice little device designed for network equipment. It comes with 4 NIC's and a PCI slot which you can plug a wireless card into. It is pretty low on memory, and the processor is slower than most smart phones, but it makes a nice IPFire machine.
It is those 4 NIC's that bothered me. I never use them. Sometimes, I set up Red/Green/Blue and put Blue on a WAP, but rarely do I need Red/Green/Blue/Orange. So, I wanted to see if I could use the extra ports as a switch, similar to some low end consumer products.
Reading some documents, specifically one from Soekris and a wiki article by Arne here at IPFire, I came upon a good, tested solution. With this, you can use as many NIC's as you have.
First, determine which ports you will use for your required setup. In most cases, you will want Red/Green/Blue, with Blue being set up on a wireless card. Do the normal install, using only the minimum you need.
As you can see, IPFire has set the first two NIC's to red0 and green0, then put the other two NIC's as the standard eth2 & eth3. These are the NIC's we will use to set up our bridge.