Reading and writing Russian is one of my hobbies. Some of the planned system updates I believe will help further support for other languages/locales. I think Gtk2 at present has what it needs to support cyrillics, but if not it will be added. I will try to piece together a how to for cyrillic Xvesa/gtk2/keyboard in the near future when I figure it out. I have only been able to display cyrillic fonts on my test system, but what is needed aside from fonts may be already present in TC though I am missing it. I am reading that Xvesa may have to be patched for to support the keyboard but I am not sure. If so, I will make an Xvesa extension that will support xinput and xkb.
Kmaps.tce may be what is needed for keyboard.