Was thinking that if your are going to change guilds with someone (eg couples) that you loose the friendship bonus. How about being able to fuse a token that is used when you change to a new guild and if someone from the old guild joins you the friendship bonus stays.
The transfer token has a 24 hour limit. If a guild is merging or a couple or friends are moving to a new guild to retain the bonus it must be within 24 hours, otherwise friendship is reset to 0.
To slow down the usage of this token the craft of it would be costly, 1 soul, 1 oth, 1 let maybe 50 perfect moonstones and takes a few days to craft, and has a limit of 1 in your inventory