I guess I must have hastily glanced over the entire message when you first sent it, cause if I had, I would have instantly voted for this ability.
But anyway, I'm very interested in this capability, and would even be interested in helping you work this into MODx as filters or transforms (I think filters might be more user friendly to the anti-geeks). I have immediate need for this capability on several current projects, and would gladly donate my efforts in working this into MODx (assuming our founders agree, and don't already have something like this in the works) in exchange for the chance to work the code into my own, and whatever API documentation we need immediately for MODx (we've got the extended API docs in the tutorials.zip and the rest in the wiki.zip that we need to decide on a format for publishing; I'll post more on this in the appropriate forum).
I've been battling with it in my spare time (ha!) for days and haven't found the proper approach yet. Any hints or tips would be appreciated, whatever you decide in regards to your transforms code.