One of the things I really like about Spotlight is that it’s easy to use XCode to write an importer for strange file types. Having written one myself, it’s extremely easy and once you done it once, there is very little effort needed to write another.
I was wondering if DEVONthink will ever allow for customer to write their own importers? That way, although DT cannot display the contents of my OmniOutliner document for me (and I really never expect it to), at least it would make the file searchable – since I could identify for DT which words it ought to add to its dictionary in relation to that file.
Another tasty addition would be a previewer API. I can see something being written in Objective-C – which is passed, say, an NSTextStorage handle – whose responsibility is to populate that NSTextStorage object with RTF text. Whatever it fills it with is what DT would display.
If I had both APIs, I could very easily write a pair of addons that makes .emlx files both searchable and previewable. Then I wouldn’t need to import my e-mail anymore, but I could index in my Mailboxes directories directly.