Quick reply...
I would enjoy seeing MicroB revived with the newest-possible Gecko engine inside.
Supporting GtkMozEmbed. Whole Fremantle is Gtk-based; it would make no sense to use Qt-*-embed.
Not Webkit. Handling 'small' differences between old-Gecko and new-Webkit would be more difficult than going from old-Gecko to new-Gecko?

Thank you. Best wishes.
If there are small tasks, beta-testing, or thorough-reading-search of code (html-markup in maps, for example) to be done, say aloud.