What exactly is the problem you're having that you think this would make easier? Is this with custom namespaces, or with the included namespaces? If it's custom namespaces, I would advise you to create BB-Code buttons for them. When you say that the standard tag is WIKI, is this just the default namespace, or do you suspect there is a problem with legacy MediaWiki code support - that is, do you have legacy code enabled, and it is parsing the tags incorrectly?