Please note that if you properly support BDO/BIDI/RTL your app will be the only powerful editor that has these features that I know of, and I keep searching for apps every month or so that support such features. Of course there are many editors out there that do support such features, however the best I have found lack a powerful regex support and always come feature incomplete.
The only app that supports these features is Adobe Indesign, think premium price. there is vim, but it is not as easy to use as an os x based app, specially for regex involving those features; actually it is mind boggling process to do a regex in vim with such features. Talk about thinking in forming a regex (naturally LTR) in an RTL context!
I noticed that your reply was poster in 2009 and almost two years have passed since then. Do you still consider implementing such features? Should I hold my breath for them? I would appreciate it if you could shed some light on the matter or give some time frame, even if stretched, if such features would be implemented.