Although we do not say how to implement Creole for a particular wiki engine, two possibilities would be to have a separate edit button, using placeholders to hide advanced native wiki markup from users or if possible to have a mixed edit where users could use Creole as well as native markup which would then be translated to the native markup.
The WikiCreole wiki (www.wikicreole.org) was set up to continue the discussion and work.
Perhaps as my last bit of BenevolentDictatorship, I've added MeatballWiki and InfiniteMonkey as potential supporters. Tacit support is not the same as actual implementation, but it's better to be as helpful as we can be than a stick in the mud. -- SunirShah