Hi Josiah,
I did create a TWclassic CM highlighter. ... BUT the possibilities with TW5 are much bigger.
The new highlighter, will need to check for HTML, widgets, macros and wiki-text. So it will be a "mixed-mode" highlighter. This doesn't make it complicated, but a hell lot more work. ... (and more sophisticated ;)
At the moment there is some work going on to create a CM-rewrite see: CodeMirror 6 [1] ... which is in early alpha.
As I wrote in a different thread. I don't think, it makes much sense to create a TW5 highlighter/editor with CM5. I think, it should be done with the upcoming CM6, once they did define, how the new highlighter logic should work.
just some thoughts
Mario