I will repeat my idea that will easily fix guild renown decay, and keep casual/new/returning players, and not torque-off small guilds:
Make a new rank, associate. An associate has access to guild chat, guild ship/amenities, basically everything that current members have. The exception is that they don't contribute renown to the guild, or decay.
So a guild could have a leader, 2 officers, 3 members, and 100 associates. The guild is considered small.
Is that fair? Sure! With only the most active members affecting the guild's size, the others can rest assured that they aren't a burden on the guild. Actual small guilds can stay at the same pace as the mega guild. It keeps the playing field even.
They can leave the renown decay the way it is. A very active member who needs to take a break doesn't have to worry about being ousted from the guild.