This is part of expected behaviour, exactly speaking kismet_server should put wlancond in offline mode and the rest of the system shouldn't be affected. This should result in WLAN being unavailable while running kismet_server but GSM/UMTS should work as normal.

That hack is needed because wlancond interferes with monitor mode. Completely stopping and starting wlancond is error-prone, so I have decided to use the offline mode way.

The only problem I am aware of until now is if you exit Kismet through the X button it wouldn't restore the wlancond status. You should exit it using Ctrl+C as a workaround of that problem.
I also expect monitor mode will break if you manually change online/offline mode while using Kismet.