Unlocking would allow Guilds to:
1) Personalize overall decoration based on player input.
2) Change weather and time of day.
3) Design battle scenarios for guild members and invited players to practice their skills on, even offering in-game prizes to keep a healthy competition.
4) Modify structures and their placement.
5) Others?
Guild members could share the load of purchasing and upgrading these features.
The possibility of modding as been proven to be highly popular from other highly successful games. Adapting this concept into Guild Halls would be a perfect opportunity.
What do you think?

Note
I've actually taken this suggestion out from a group of others in this thread that has to do with making Anet able to cover expenses with improvements that goes beyond their ability to respond within their no-monthly-fee concept and thus sparing players from having to veeeery patiently wait for a new version of Guild Wars. Can the franchise survive the wait for another upcoming Guild Wars version 3, 4, 5... with the next cool or useful features that players keep asking for? There's a limit to anyone's patience and I would hate to see a really good concept and game waning away into oblivion...

This suggestion had the most enthusiastic reaction, so I figured that it would deserve its own thread for discussion and input from the community, without a complete bias of money talk that would reflect on our meager pockets.

And I DID search for other threads, as requested from the moderators, but I honestly didn't find anything where I could place this idea without being somewhat out of place.