@jessegrosjean, I don’t know if you had a chance to see how Brett use the URL Scheme to implement themes in his last Marked app; but it is just phenomenal. This is the excerpt of the documentation that mentions the implementation.
I’ll need to document this one further, but there’s also a new method in the URL handler that lets you add a new Custom Style to Marked via a link (x-marked://addstyle?name=My+new+style&css=[url encoded CSS]). Just pass a name and the url encoded CSS and a new file is generated and added to the Custom Style menu automatically. This should make sharing styles even easier. I’ll be sharing an updated StyleStealer bookmarklet very soon to allow a one-click way to duplicate styles from your own sites into Marked for previewing.
This would be a great way to add themes into TaskPaper and WriteRoom, and maybe extend the idea into other aspects of the programs. If one could add scripts this way, it would be pretty amazing; but I understand the security problems.
Anyway, just mentioning this while I know you are working in the code for WriteRoom.