Sick of this recurring illness now.
Updated my VBox installation earlier and my Debian VM in the hope that I can resume work on this again very soon. I noticed in the fremantle-gtk2 repo that you have removed the GTK module and opted for a forked GTK instead. Were you hitting a roadblock/problem with the module method?
In terms of GTK3, I know the module method will not guarantee 100% compatibility with the existing Hildon API. GtkIMContext related code, as previously mentioned, is a no go due to being unable to access the context. This leaves me with a few choices, do I keep as much API in tact as possible or ditch compatibility like in my original attempt and create a cut down or API incompatible library (like with GTK2 and 3), following the deprecation messages left by the original devs.
Another option would be to suspend work on hildon-desktop GTK3 and instead add GTK3 support to the fremantle-gtk2 environment.