Reselling VoIP / FreePBX

We are a small ISP and would like to offer our residential and business customers VoIP. We have FreePBX working with one trunk.

It appears that FreePBX would not be the appropriate tool for us as our customers would all be extension to each other. In general, FreePBX looks like a great tool for a single business.

I am wanting opinions about using FreePBX to resell VoIP.