A modded server wouldn't work, the developers would have a huge workload due to developing 2 different servers at once and there is also a great chance that the population will be low due to people not wanting to download mods to play. It would be cool to test out to see how it works but it would take super long to get it up and running. They would need to spend more time and resources to make the server which will also decrease the frequency of updates on our current Altis life servers.