Yeah, that is possible. I'd still do it manually, but remotely.
I believe this will do it. (easy enough to test in any browser)http://yourServer:8000/admin.cgi?password&mode=kicksrc
obviously substitute your shoutcast server IP, port number and password to whatever yours is.
Or you can just visit http://yourServer:8000/admin.cgi
and you will see the option to kick the source in there as a link you can click.
Now the thing with this is, you set your remote nicecast to reconnect rapidly, and you set your distant studio nicecast to reconnect slowly. This way, to kick, you start your remote nicecast, initiate the kick by visiting that url in a browser, and your remote nicecast will connect in ahead of the other one.
To adjust how fast nicecast connects, look in the docs for the advanced settings for nicecast. You can edit a filename I can't remember the name of and enter the time intervals in seconds for reconnection. Set the studio one to long intervals, like 10 seconds, and your remote one to fast intervals, like 1 second.