It is already done in Quebec. there is about 15 repeater linked to a private network by VPN and all the repeater are running plain vanilla ASL. The sysop of those repeater dont want inter connection to the outside and it is perfectly fine like that.
They use fix IP adress in a class A
10.0.0.0 to 10.255.255.255 network and the vpn take care of keeping this all linked even if the internet connection change IP adress. They even have a script that download the configuration files from an ftp server every night so if they want to add a repeater they change the files in one place and they all get new files in 25 hours then when the change need to be live they send a reload command to every repeater by a small script that connect by ssh then go into the asterisk cli and issue the reload command.. Since they are all on a local network an operator only need to connect to the vnp and he have access to every repeater .
The server is a vps in a data center. it does not even have asterisk on it.
A few years ago there was a project to do a kind of parallel ASL for the french community. but it never was done.
Pierre
VE2PF