500 ? That Does seem excessive.
Suggestions:
Limits on the number of people that can be in a clan? (I'm sure that's not a new idea !)
Limit the amount of builds on any parcel of land,
Adding a way to give building/usage permissions to allies.
And of course,
I support the idea of a Limit the number of claims of any one person (particularly on PVE) Maybe start with 2 and add an upkeep cost with gold -- you could go 2-3 weeks out with the payment, Make crafting a new claim something with high mat cost. But seriously the idea that 500 clan members with unlimited claim flags is just stupid. What new player could ever find a space at that rate.