That's something that can only be done by staff and may require some back end tinkering, from what I remember hearing a while back. I do agree that we should have more release regions, though. Hong Kong, South Korea, Taiwan, and mainland China are all at the top of that wishlist for me since there are far too many games exclusive to those regions at this point slipping through the cracks on the wiki because of existing limitations. I'd love to add a bunch of PC and Famicom ones to the database, but release information would otherwise be rendered blank and have to be added manually to the main wiki page or something, which is a bad workaround for something that should be done at a system level.
I'd also like to see a "Language" field for releases too. This has the potencial to get very complicated though, as there are probably so many language specific releases for older games in Europe. One step at a time - additional countries would be a start.