Modding zipl will be no fun task (well, at least zipl.c anyway...common.S was quite fun and is ready to go) so I thought I'd get suggestions up front and not have to redo for anyone.
I guess what you should do is support a number of IPL sections identified by something of 4 bytes, say a number of 'slots' in the IPL record. Either learn zipl how to put things in these slots, or use a separate userspace program that can copy the first entry (written by zipl) to one of the others. And you probably could have different slots point to the same image but use different command line.
Rob
