I ran a fell based Ultra a few weeks ago, the pre-race info was very strict about what must be carried. Lo and behold, no kit check whatsoever. I was very surprised.
Got to be realistic about logistics and its easy for me to theorise as I've never (yet) organised a fell race, and in your average evening summer shorty it could be construed as overkill. In short races, the exisiting rules of RO discretion works just fine. But I would like a scenario where in races over a certain distance, lets say 12 miles, a kit check table is in place and EVERYBODY gets checked. The Edale Skyline setup works really well. Same at Nine Edges. And if you haven't brought the kit, you don't get to race. Simple.
And on the short races, if a runner isn't complying with whatever the RO has stipulated, then yes, some sort of penalty should be applied. A DQ seems fair. Perhaps a list of race DQs in the preceding months in the Fellrunner would encourage people to just do the simple and fair thing and carry what they are asked to? I don't think not carrying the kit when asked to necessarily hands the runner an advantage as such, I just think it demonstrates a lack of respect towards the race and the RO.
With respect to Sore Legs' opinion about the clubs though, I don't personally think there would be a lot of merit in punishing an offender's club. It's not Dark Peak's or Porter Valley's fault if I flaunt a RO's rules. I know what I should be doing.