To add insult to injury.... If that someone is a kid with a less than enlightened mother, the sponsors of said contest could find themselves with a very ugly lawsuit on their hand as they set up a contest in such a manner that people would be encouraged to push designs to the very edge.
That's an argument against this site running any sort of contest whatsoever, but not against this one in particular. Considering that the proposed rules would favour very small, very efficient designs, it is miles ahead of the last contest in terms of the level of expected safety. Last year's "penetration contest", or, more aptly, the "fuel/air PVC fragmentation bomb contest" didn't result in any fatalities or serious injuries, and I still suspect it of being consciously designed to cause them
I disagree with the premise that this idea encourages unsafe practices. Considering that building an entry would be almost certain to cost more than any prize that could be mustered, it would take a special kind of idiot to build one which was likely to fail in the attempt, even ignoring the obvious risk of personal injury. And really: "... a kid with a less than enlightened mother..."? You suspect such a person to be capable of building the kind of launcher which would rupture steel pipes violently enough to cause injury or death to himself upon igniting it remotely? Big, dubiously constructed hybrids would be so entirely outmatched in this contest that none would be built.
Now, onto the matter of ETGs; they're not at as much of an advantage as some may think. I can think of only two existing ETGs which could rival HyGaC20 in terms of energy density, and one of them was built by Larda. To beat SCH160 steel hybrids, I suspect that an ETG would have to use machined parts, thus removing it from the category altogether. Similarly, an ETG to beat a machined 500X oxy/propane/helium hybrid would not be an easy ask, even with extensive available tooling. I've built a lot of ETGs, and it's my qualified opinion that their inclusion requires no special rules whatsoever.
Spudfiles' resident expert on all things that sail through the air at improbable speeds, trailing an incandescent wake of ionized air, dissociated polymers and metal oxides.