I know there are internal Guild Points .. but this Guild Points are more used to get an eye on the Ranking inside of that Guild .. but if a Guild can earn (external) EXP like a character can .. there might be some possibiliys.
1.) there is a opinion in each Guild to earn that Guild EXP which gave the Guild a purpouse
2.) there is a way to have an eye how active and prospering one guild is by that way
3.) this Guild EXP could be used to rank up in political influence of a Guild
4.) This Guild EXP could be used to \"buy\" a Guild home if maybe a Guild has enough EXP and money it could buy a Guild House which prevents that each new Guild gets an abandon new home
This Guild EXP might be earned in several ways. Maybe the most think about \"yes a Guild war\" (why you always wish to play war

) .. i more think about Quests which could be implemented by other Guilds .. as example a Guild creates a quest for other Guilds to help in some way .. maybe that a mage Guild ask a warrior Guild to kill some tefusangs which killed some mages on their way to City Ojaverda. The Warrior Guild may be rewarded with those Guild EXP. Or that maybe an Evil King (NPC) claims to start a war if the City of Ojaverda is not paying 10000 trias to him .. that way a Guild could be hired to prevent that war by using political influence or a Theaving Guild might try to kill that king or maybe just the earn enough money to calm down that king.
Another Quest might be to fight a dragon or quests which improve the activity between guilds .. like one Guild XXX has to get some stuf from another Guild YYY and deliver that to Guild ZZZ .. or maybe something in conjunction with the Temple of Laanx or the Library. That means that there are official Guild Quest and Own made Guild Quest).
The earned Guild EXP might also be use to train internal Guild skills .. like to get one member in the Guild be trained in the \"training skill\" with that EXP ..