Daverobo

Hi All, i was thinking about a co op mode on gta4 and was reading but couldnt find anything about it, gta4 is multiplayer so i think it is possible but do you think they would do this and if so wot would you think of it. Like 1 Player could play as niko and the other as his cousin. Also how do you contact rockstar because i would love to ask them about it.