Nice bit of work James, and useful. In the last 2 weeks WPMU (the software that runs this site) has gone through an extensive reworking of the mod_rewrite rules, with some pain I can tell you!
I think the rules are just about there now and give an added benefit. All “unknown” requests are sent through mod_rewrite now, so what I may do, right at the end of my mod_rewrite ruleset is have a catch-all rule that sends requests to my solitary “pages” script, or in other words, it does the same thing as the ForceType stuff but should be more portable I hope!