I applied 3 patches from Fedora 22 for Gnome-Terminal 3.16 and VTE3 that add:
2. Dark / Light theme switch
3. Terminal Notifications.
The issue is that I'm not sure I can write proper PKGBUILD files, plus on ArchLinux IRC a guy said that those patches are likely to break due to VTE.
Anyway, if someone with more experience than me (which I have 0), wants to AUR them, here they are: