The original word for Hourin is 法輪 "Law Wheel", a reference to Dharma, meaning the laws, nature, teachings of Buddhism. Because they considered so important and sacred, that's why the kanji can be changed 'Treasure' Wheel 宝輪.
As for the gateway thing, it is a huge plot hole, if all you need is a bunch of souls to help you open it or they open it themselves, then you just need to gather enough Saints or hell Athena for that matter, and it's done.
*NOW* Hades won't just sit on his ass. He can use the Evil Stars to find other people that can be turned to Specters. But the Athena-Hades War would totally be a Spam War with no real fighting! XD
I like this Virgo story but Shiori is getting tired??? All she need to do is have the ending be Asmita figure out the way to seal the Specter and it was this fight that led him to the method of the building the beads... Maybe she thought this was way cooler and dramatic...