We have a tiny bit of room for more, but the furnishing inventory slot limit (1000) will need to be less than or equal to the house slots limit (750)...
1) The top 50 guilds by total achievement points make the list.
2) Only the top 500 characters in each guild that have played in the last 7 days are...
Yes, your character will only be able to become a standard character at that point, but you'll lose nothing (no level loss, badge/title loss, etc.)....
We'll keep this in mind for future jewels, but I can't justify changing it after players have acquired them. You said it yourself, if you don't want...
I'm kinda torn here because I want to keep a reason for you to visit towns, but I can see where it might be nice to have a leaderboard in your house...