> My main concern is related to the handful of serious business people who
> come through. These people tend to be reasonable, relatively computer
> savvy professionals who expect unfettered access to the internet.

If they're that "serious" then they'll have their own means of making
connections to the internet. You're on a fool's errand if you think
catering to these folks will buy you much. You're far better off
maintaining a stable baseline of basic services. Just doing THAT is a
full-time job.

Port forwarding from the outside-in is less than trivial if you want to
connect inward to more than just one computer. It involves multiple
external IP addresses or internal proxying systems (and this is GREATLY
oversimplifying it).

There's also a good no-tech way of dealing with bandwidth abuse. Throttle
their connections such that it looks like the service is unreliable.
Pretend incompetence when they come calling to bitch about it. Sometimes
it's better to have them think you're a fool and the setup is worthless
rather than have their abuse drive you crazy. This is assuming it's a
"free" service. Once you start taking money from folks for it your
headaches enter a whole new range of complexity.