well i think it would be awesome if peoples could enter other peoples cars and drive with them, like in SA:MP
so i would be more gangish.
(gangs-war)
you should make a territory game mode (like in gta sa) that each gang got its own territory (in this case island) and need to protect the gang hall (in this case the place where the gang leader is it) and to go and takeover other territories,
the main objective of this game mod is to kill the enemy gang's boss.
(cops and robbers)
this game mode is actually the same like in SA:MP, there are a group of cops that are fighting against other players (criminals) for example in SA:MP theres a server called "Crazybob's Cops And Robbers", now this server is one of the most respected and best cops vs. robbers server there is, because you can do everything in there, work as everything you want, rob shops and kill people, chase after most wanted players.
this is a perfect example of my idea.
i wish those would be in liberty unleashed xD