HTML composer: Did you consider using Fckeditor? I checked the archives and I saw that there was a discussion about that in Oct 2005, and the conclusion was that the goal is to support plugging any editor with plugins API, what's being developped. What's the status of this? I used both TinyMCE and FCKeditor and I prefer FCK.
JS interface: Did you consider using a JS framework? I've been working quite much with prototype and after that JQuery. My personal preference is JQuery, based on experiences. Rewriting would be a big job, but could be done continuously, during the process both packages would exist. There are some benefits, I think even the code would become smaller, and pre-created interface plugins could be used. (And the packed version is just 16k.)
What do you think?
balázs