Gajim will never be considered for KaOS. There are already quite a few options for voice/video chat, so a Gnome/PyGTK based client will not be added. Let alone that for the features you mention to work you will need to add dozens of python packages, a good part of the Gnome desktop, and it needs the complete obsolete gstreamer 0.10.
Tox (qTox) is a very capable Skype replacement.
Pidgin and Jitsi are XMPP options.
So for you to have gajim:
https://kaosx.us/docs/package/