Many players at Skybase use invisibility potions to sneak into trading rooms and intercept trades/steal. I am suggesting that the use of invisibility potions be disabled at Skybase. Let me know what you think.
I'm not sure if it's possible programming-wise. I would want it to be like dirt block. You try to throw it down and you can't.
That would be nice, but I don't know about ability to do that. Also, would it be able to just then off the effect as soon as you entered sky base? Because if not, they could just drink it or splash it somewhere else.
Actually, you can do this with vanilla. First, set up a clock next to a command block. Inside of the command block, put in /effect @a 14 0. There are several downsides to this method, however. One is that this would make invisibility impossible everywhere on the server so long as there is someone walking around in skybase. Another downside is that this clock would add to the many others to create just a little bit more server lag.