for a rig you are usually dealing with keggles or humongous pots, so you may want to make sure they fit on it and can get enough heat to make it worth using. My thoughts are that it would be more trouble than it's worth for your main brew kettle, BUT I had another idea.
I do a lot of decoction mashing. In my brewhaus I have my single tier three-vessel two pump setup. I also have a glass cooktop my brother pulled out of a model home for me. I pull decoctions from the mash tun and use the cooktop to boil them. I also do my small stuff on those burners, like making starter worts and pressure canning them, heating up a pot of water for cleaning the rig, etc. It's very handy having a regular stovetop for those uses.