You're correct there are no hard rules in regards to feet design, other than having them placed opposite the dogs path.
I prefer sets with a foot on each pole for stability reasons. I think after the jump adjustment we recently made, and the tunnel bag adjustment we made, if we required clubs to purchase weave poles as well they might possibly plan a mutiny.
This would be something where I think the exhibitors should express their concerns to the club directly, and see what their response is.
It's something that could be mandated, but it's probably a long ways down the road. Need to let all the clubs rest a little bit financially for a few years