Recently I had to make a bunch of syntax definitions for archaic languages, so I made a plugin to help me out. I figured I'd upload it in case anyone else finds it useful.
It's VERY primitive, don't expect magical embedded references or syntax definition repositories inside of files, it literally does the bare minimum:
The basic description, name, uuid, and scope
The Patterns Array
The Match/Comment/Scope inside of the patterns
Basically, you press ALT-CTRL-6 / ALT-CTRL-7 (depending on if you're making or editing), and then answer the questions at the bottom of the screen. It will either completely make a language file/directory for you, or it will edit the one for the file you're currently editing.
That being said, I'd love to integrate in the ability to choose the scope of each regex from a colored list as well as have the advanced features, but the time required to get that far isn't in the cards right now. Who knows, maybe I'll get to revisit it in the future?
In the mean time, if you find it useful and feel like working on it, feel free to let me know and I'll figure out how to admin/organize that.