How do I add support for another MIME type in G2?

I started a thread here a while ago, but got no answer on how to add a new MIME type, so I am starting a new thread.
I am trying to add support for playing DIVX using the DIVX web player - I can hack support in (see linked post) but only by modifying the AVI MIME type as i could not seem to get it to recognise a DIVX from the MIME type (should be 'video/x-divx')

If anyone has info that could help, please let me know - I would like a decent solution that can potentially be folded into G2 for all to enjoy.

Also, if anyone would know how a way to give users the option to select whether they want to use the DIVX player or a user's associated player, that would be great. Apparently there is a DIVX web player for linux (mplayer) but it can be a bit problematic to set up, so it would be nice to be able to set DIVX web player as the default player for DIVX, but users have the option to change that.

Peace, out