Passive guild skills.

Simple ones that make a difference when ranked up. Buffs that elixirs would give, but very slightly only. Max level could give half of whatever the gold elixir multiplier is.

To level-up the guild, could be that only players at the elite level can do so, or there's a rank which automatically converts gained XP to guild XP.

Only the guildmaster can assign points. Plat for respec of guild points.

This would only apply if your team is full or majority is your guild. PvE maps, 3+ would activate these buffs. None in PvP.

Just throwing ideas out, main point is guild leveling.