I have two 7200s, one has a PRI and the other is networked and uses those trunks.
I know mobex won't work from the system on the far side of the VPN, but is it possible to have a button forward inbound DID and direct dial calls back out to an external land line or cell?
Possibly fixed call forward?

Thank you in advance!

As long as the calls ring direct to the station. You can set up the Forward all in 102 and set it to the external number. This will be in effect until they turn it off.

Regardless of internal dialed or external did?

Also can I make a button to set it?

Yes, just make a button for FWRD1 and it will set it. Then in 5.14.6 you have to set intercom external forward to on.