I am wondering if you are aware of pWhiteboard (http://chxo.com/pWhiteboard/). If not, please visit this site and look it over for possibilities. Seems like a nice use of HTMLarea and PHP. Also, this person references a patch for HTMLarea 3.0 source at http://chxo.com/pWhiteboard/Installing_HTMLArea.html.
I like the idea of having a bigger HTMLarea within a page, rather than using the enlarge popup window feature. In looking around I've noticed others are not including this on the toolbar, perhaps because it is the same pain in the ass as this bug Martin has reported.