You wont find any remote access products support.... VNC will work fine. I have used it with Unity, SQL, Exchange, and other MS products... Just remember, if something goes wrong, and the server ins 1000 miles away.. you are in big trouble. That is why upgrades normally call for an admin to be at the console. If you are upgrading from 4.05 to 4.1.1, I would say go for it. If you were going from 3.x to 4.x... I would be at the console to do this type of upgrade.
We use an IPKVM that works great. I have used products from Vector Networks (pc duo) and this works great. Usually stay away from PCanywhere, but it does work as well.
Just have a backup plan in place. And do not use Terminal Server for ANY type of patching or upgrades to a windows server or Unity patching/updates. It can get ugly.
hope this helps.
tc