Using GUP on a private network

Hi,

We have a SEPM server installed in our site, everything is working fine. Then we have another network with a few computers that doesn't have access to the SEPM, except for one.

Could we give to that computer GUP role to update all the client that doesn't communicate with SEPM or should I install a fresh SEPM?

By the way that network doest have internet access.