Why not let a VIP player sort of "deputize" another player. That player can then accompany the VIP player wherever he/she goes. I havent actually used the guest passes but from what I've read they don't seem very useful. The mid level quests take too long and the lower level quests, well, 30 points is fairly pricey for some quick noobish stuff. If VIP had this ability, I'd buy it in a second, as it is, I'm debating on just buying some adventure packs or none at all...
So how to implement it? Like a buff or something that lasts one hour on the other player and can be recast every 50 minutes-hour, whatever. So you can only deputize one player.