Did you see the bottom of the page at http://www.icecast.org/docs/ices-2.0.0/inputs.html
I've never used it, but I've read the script option only cares about the first line of output from your script's STDOUT
You could write a more dynamic script that generates an entire ices config file (no repeat option). This parent process could create a config file, spawn ices, wait till it's complete, and repeat the cycle. The downside is you wouldn't be able to crossfade between tracks if you needed to.