You could say that Guild Advancement mod, plus Fighters Guild Quests and Mage's Guild Quests from David Brasher, plus Bane's Guild United for a guild looks overhaul, go a long way in enhancing the guilds in Oblivion. Not a lore extension or story extension, but makes climbing the guild's ladder more difficult for a non-specialist character.
Also, Integration-The Stranded Light quest mod includes a full blown guild of its own, if you manage to follow the questline into completion... never got there myself, but I've seen/read others that have.
I realize that this may not be what you're looking for, but I'm just posting them here in case they interest you...
Here are the links:
http://www.nexusmods.com/oblivion/mods/42870/?
http://www.nexusmods.com/oblivion/mods/41012/?
http://www.nexusmods.com/oblivion/mods/39591/?
http://www.nexusmods.com/oblivion/mods/42261
Integration ->
* Choose one of these (read the instructions!):
http://theelderscrolls.info/?go=dlfile&fileid=441 <-- NO requirements version (doesn't depend on having installed Less Annoying Magic Experience or Race Balancing Project)
http://theelderscrolls.info/?go=dlfile&fileid=349 <-- It has dependences, must install LAME and RBP first.
Hope you find something you like!
Best regards,
Leandro