That is what I have gone with after a bunch of playing around - it is not exactly what I was thinking. But it does work.
We were only looking at doing it with 07 numbers on the plan (we also have 02, 03, 08 etc that we deal with) - I come from a 3CX background, so the outbound rule building requires a little bit of a shift in how I look at them.
Thanks for the help!