Frankly I have to question whether there's any benefit in this, given that a) probably almost no one will have occasion to use more than one wiki package more often than once in a blue moon;
I'm strongly in favor of a common markup standard. MediaWiki may be the leading wiki engine on the web, but it is only one wiki engine in the workplace. At work, at SAP, each day I have to deal with MediaWiki, Confluence, Socialtext, Twiki, and some other random engines. Switching back and forth between the syntaxes is a huge pain. I avoid it as much as possible, to the detriment of getting my work done.
Dirk