Create a functional library with all the stuff we need.
Make a GObject for session management. If that all works, (core) applications should implement it, see step below.
Mainly a task for easy individual developer, to port his/her application to 4ui. This also means your apps need to port to GtkBuilder.
Status: Depends on each component, completed for core modules
GtkBuilder works fine with XfceTitledDialog, but this only works if the library is properly linked, see Gnome bug 588238. You can work around this using something like this:
if (xfce_titled_dialog_get_type () == 0) return;
Status: Depends, probably something we have to live with until Gtk has a good proposal.