Well, I don't really care if it's easy or not, I have other distros to use meanwhile.
- If you'd like to do it too, just install any gtk-based distro, use us-intl keyboard anf put export GTK_IM_MODULE="cedilla" in /etc/environment (~/.bashrc didn't work for me) -
Plus, I use Firefox and Thunderbird. I can live without this weird cedilla even in there with the tip above =D
Maybe it's time to talk with the KDE team as well