

Many admins say it is a lot of work and they put a lot of effort, money and energy in it. Some even close their instance after few years, because it is just too much.
I would say you should limit the number of active accounts. Probably to a few hundred at most in the beginning. Close registration when things start to become too much. Re-evaluate periodically and re-open as necessary/desired. There’s no reason you have to allow thousands of people on your instance.
How will they detect “VPN traffic”?