This took quite long as openSUSE 12.3 does not work as expected inside SUSE Studio and I was too lazy to find all necessary tweaks earlier. The same problem actually prevented from Weblate 1.5 being there at all.
The biggest obstacle was MySQL setup - after enabling "Set up MySQL" in studio, you end up with MySQL database with empty mysql.users table, which obviously can not authenticate anybody. As I've found out, the only way around is manual setup.
Once this was figured out, the appliance only needed minor tweaking and is now ready to use in SUSE Gallery in all formats used for virtualization.