Wow, I forgot to respond to the questions at the bottom of your post
What other things would you like to see? Would you like RvR battles that were heavily focused on guilds? Would you like to see some GvG taken place? What about dungeon raids? What would you like a guild to be able to accomplish, and what featuers would you like?!
Guild vs Guild would be ok, I feel in cases like DAoC, where there is an arena, zone or seperate place for it. That is coming from the PvE perspective. On a PvP server, I would say it'd be even cooler, minus the Zone restriction... though Arena's always seem to interest me. Even a futuristic game like AO had an Arena for PvP battles.
Should those PvP instances be heavily focused on guilds? I don't know... I want to say no, but on the other hand keeping guild statistics are cool. I like Mythic's way of handling DAoC's guilds, A LOT. I love Mythic for one main reason: All their gaming stats, are available via XML to retrieve for use with an XML aware website. Case in point (have to brag) look at:
http://daoc.runs-with-scissors.com/ ... the news, the alliance list, the crafters and members rosters, the Realm Points, and Realm Ranks are all available on my guild website utilizing XML feeds from Mythic's servers. I don't have to update the stats, and neither do my members need to update their own (ie: Guild Portal). I think PvP may have it's areas... Clan vs Clan, Guild vs Guild, Great House vs Great House.
Dungeon Raids? Make them available to groups of folks, same guild, clan, greathouse or whatever.
I'd like guild's to be able to earn points in some fashion, both for PvP and PvE servers. See Dark Age of Camelot on how to do this successfully (DAoC's Gaheris server is a PvE only server, no PvP except /duel).
~ Jaraeth