Dragonephobe maybe typing /ping (username) and then it gets on would ping you when that user gets online or there could be a pingpermanent which woud ping you every time they get online (instead of just that one time) This would be extremely helpful when waiting for a player to get online Im not sure if there is one
I can see this working... if possible. Friend list limited to 5 for Builder, 25 Resident, 50 Mayor, 75 President. EcoDollar purchase to get 25 more at any rank.
Problem I see with this (if made a donation feature) is that Mojang could very easily add it as a feature in the future. CJB has a chat pinger that will ping on words you choose. Not the same for when users get online, but if they usually speak right after coming on, you will get pinged by their name. Or, you should... I don't use the pinger that often.
Use the cjb chat pinger, have you and your friends all choose a word that is rare (like potato) lol, and type that as soon as you get on everytime.