You should really have a look at KPart and its internals. All the problems you describe have been faced and solved by KDE.
I understand the component activation is quite tricky, espcially if you plan to have two components displayed in a widget. Get in contact with David Faure and Simon Haussman (or simply kde-core-devel) to see if they can provide you some insights.
New HTML Parser: The long-awaited libxml2 based HTML parser code is live. It needs further work but already handles most markup better than the original parser.
Keep up with the latest Advogato features by reading the Advogato status blog.
If you're a C programmer with some spare time, take a look at the mod_virgule project page and help us with one of the tasks on the ToDo list!
