I have no my own themes, all themes are taken from ace sources. I run build script (comes with ace sources), it merges files (and inserts css to js). So, you can fork original ace repository, create your own theme and run buld script (requires node.js with some node modues) with `full` argument - you get your theme file in build/src-min-noconflict/
I have good news for those, who uses Ace instead of external editor:
1) I have added live php syntax checker
2) ace devs work on code completion feature
In general, it is possible to turn MODX into online IDE with almost all useful features. Just take a look at the
Cloud9 IDE
But I am not sure MODx CMF, MODx core team and MODx regular devs need this.