Guys, this is a very good idea. Thanks for starting it.
Maybe I must have missed it, but don't you want to rate the tpf members too? There should be like a feedback or rating for those who authenticate the items going to be posted for sale. I.E: A, B, C authenticates a Chanel bag. If the seller agrees with the outcome and has records to support it the outcome, then depending on the result the bag will either be posted or not. Successful posting on the site (not successful selling) will give the seller an opportunity to add positive feedback to A, B and C.
For the authenticator, there should be different levels set up (junior=new member, authenticator, senior authenticator). When junior authenticator receives certain number of feedback, they should be able to move up. Authenticators cannot authenticate their own items to be posted for sale. And there should be restriction on authenticators authenticate each other items. Confuse enough?
Just a point of view from a potential buyer...

I need to be able to trust the authenticator.
I dislike
eBay and paypal too. I rarely sell stuff on ebay, except for the time when dear husband forces me to clean out my closet... I recently found brand new Juicy couture, Coach bags, Prada shoes that I have bought a long time ago but never got around to wear them. It's like finding treasures

Some of them I need to sell, but I don't want to deal with
eBay and Paypal.
I'm in the IT industry and will be more than happy to help out. Please let me know if you guys need to reach out to me.

Though I'm new, I'm not a part of
eBay, have no ulterior motive other than researching for my next dream bag.