We'd have to find a Valve artist who is willing to commit a lot of time to detail a map.
And seeing as Artpass can take a lot longer than layout development, I wouldn't be surprised if no one was free to do it (or would want to commit the time). It'd just be time that could be used on something else more important to the company (recently released game, Un-announced games, etc).
Also, when you're designing a layout, you have a specific theme in mind. With that theme in mind, you design your architecture and geometry around it. When you try and use another theme on it that wasn't originally intended, things just start to look weird. The original artpass was nice, because the layout was just really generic enough, it could be artpassed as anything. But, getting a generic layout like that is a lot harder than it appears.
I'd also suspect that Valve would be more cautious with the layout, since thats the finicky bit. You can detail it however you want, but the gameplay really needs to be GOOD ... really good .. and generally that is tough.
tl;dr: Reverse artpass is a neat idea, but I don't think valve would want to commit the time to artpassing ... and it'd be risky on the actual quality of the gameplay.
It would be a very neat idea, but if we had this type, it would be more viable to choose partners and make a collab, one designs the map and the theme, the other makes the artpass. But considering it would take about 9 months, it would be just too hard.