This would only be dangerous to people investing in new magic product, which doesn't seem like a worthwhile endeavor for them to be doing anyways.
I think it's a cool idea, and a nice easy way for them to print things like fetch lands without having them in standard or other limited sets. If there were a box set of the 5 enemy fetches for $119.99, for example, i'm sure people would pick them up without destroying the market price on all existing copies.
I'm sure most of you are aware, but Modern Horizons has "art cards" which are essentially just full art cards with a blank back for artists to doodle on. I see some noise already that people are going to use these as proxys for the high-dollar cards for playtesting purposes or in casual games for the more expensive cards. Wizards could easily do this for Vintage cards and sell as "art" cards.
I still think at the end of the day, players want a supported format, and a healthy format (however that is defined by the masses), so not sure having more proxies will grow the player base.
The best way to do it is look at your collection, come up with a number ($15K?$20K?), and then just stick to your guns until you get what you are happy with. Expecting to price individually and not get offers at only 50 to 60% of it will be tough, especially since the Old School market has cooled down and most likely wont pick up again until March/April/Tax Season in the US. I can quickly flip through my "brag book" and quote a number that I'd part with the cards for; it's all just cardboard anyways right? 
Disregard my directional question, I saw you just said North of Pgh. We typically play at Legions in the North Hills if you ever want to jam some vintage. Just give us a couple weeks to make sure the vintage guys are there.
@popedeuce37 which part of Pittsburgh are you generally from? i.e North, South, East, West? Me and a buddy have fully powered Vintage but we don't bring it out as we are typically playing old school or legacy most FNMs. I talked to Ron (Mr. Nice Guy) at EW as well, and he said if we could guarantee the 8 players more often, he'd consider doing Vintage at least quarterly again. I haven't had a chance to talk to him since then but plan on stopping out soon. He is strictly sanctioned but I wouldn't mind doing proxy stuff somewhere else if needed.
No changes, and no commentary on thought process this time around.
Next announcement will be October 1st, 2018.