Don't reinvent Yet Another Markup Language. Consider three tiers of interface:

1. stupidly simple handles 80% style markup language
2. XML for complete access
3. Perl for the powertools dudes

It's tough to come up with the first two, but if you do it right, you can advertise your site as "configurable without any code". XML is preferred for a complete language, because it seems to be the data-representation language of choice these days, or at least gets a lot of buzz.

-- Randal L. Schwartz, Perl hacker