Sadly not so much progress
This week I had some other "undelayable" things to do, so in the middle of the week I was almost offline. That's why there is not much to report.
When I was able to work I was still busy with the window manager, then I tried to hack the next available modul (the control center), which was actually dependant on the new window manager, so I got in a dead-end. (and by the way I successfully screwed up my local repo without commiting the changes, so I lost a decent amount of work. Congratulations to myself.)
By the way there is already a user with GTK3-ish MATE terminal, which is awesome :D Although it is buggy (surprisingly?), it is great to see someone already using my code :) But I'm already afraid of bug hunting in the whole desktop environment... :D