Contracts would be cool. You can really sign up for jobs, for example, you want a player to do jobs for you, like bodyguard. You give him a contract ( made with some options ) like filling in how much he gets each hour/day whatever. and what the consequence is when he doesnt obey. If he walks away and doesnt do sh*t, you can buy a hitman which will only work because of the contract ( so you cant send hitmans for everybody you'd like to see dead ). And you will get your money back, or whatever is left of the money.
When the contract is in progress the bodyguard or whatever can walk up to you and start his job by pressing o or whatever button. You can accept with the same button. Then he is working for ya and he gets payed for the time he works.