Consider that a proper replacement for MicroB UI should work with browserd and mimic any feature present in actual app. I consider that an open replacement for the UI would be great news, but bringing it to a good shape won't be easy. Considering that it's your first time with Maemo development, my advice is to start first with something easier to achieve. You could start trying to make a good port of Helium web browser from Meego/Nemo. It's actually a working browser based on QtWebkit and would be a nice improvement over actual choices.