We'd need proper exchange rates though. If I sell 100m galder on trickster for 100 GGg, then I expect to get 20m on latale for the 100 GGg, etc. Also since the system would be only for members which would make it hard to market properly.
I'd say one of the biggest problems is accessiblity, how would I get the GGg for the trickster galders? Do I give it to a mod or something? The same issue would apply for selling GGg, there isn't really a good system for that kind of thing.
If the staff can think of a proper transaction, I'd say it'd be a great idea.