See Rift.
Guild completes quests, gain guild xp. Guild levels up and gets skill points. Spend points to unlock useful abilities for the guild.
Quest examples:
-Kill 500 players
-Complete 30 flashpoints
-Complete 10 operations
-Win 40 warzones
etc.
Perks
-Guild summon (rally banner), ie. summon guild members to a planet, 60min cd
-Guild local buffs (requires a consumable), ie. +5% damage for 20 seconds, 60min cd
-Faster mission time, increased crafting crits/RE, better returns from missions
-Loot more credits from corpses, increase chance to get items from corpses
-Global (passive) buffs like +stats, +expertise
-Guild social perks, ie. special emotes, special items, flare
-Your ideas