Your last idea is what would work easiest and cheapest.
Our local repeater is sited at the local TV station - nice antenna height. However, we did not want to approach them about tying into their local network for Internet, since we are sure they would have security issues (as you do). I wanted EchoLink connectivity through the repeater, so I set it up at my home QTH, about 7 air miles from the TV station. All I use is a dedicated Windows PC (nothing fancy) to run EchoLink, an FM transceiver on the same frequency as the repeater (normal offset and not reverse, with appropriate PL tone), and an interface box between the PC and radio (for audio and keying). Setup an EchoLink account and use the -R (repeater) designation. I have the radio running at low power (5 watts) fed into a 5 element beam pointing directly at the repeater. The Internet connectivity at my home QTH provides the EchoLink access to the repeater remotely. It all works great!