> How would you transfer ownership of big linked data structures?

Very carefully?

More seriously, I think with guilds, what you absolutely don't want to do is build yourself into a position where you ever want to move a big linked data structure (that is, unless you know you are only going to use it in one guild, you never want to build a big linked data structure of mutable objects.)

Big structures of mutable objects should be guild local (or external, in a store that has its own controls for concurrent access.)