The advantage, for companies involved, is that you can have much less square footage but much more exposure, by putting together little islands.. As well as having demo time on the tables, what have you.
The disadvantage, of course, is having less square footage, not to mention the cost.
For anyone to invest into the idea, publishers and/or private party wanting to use it to make money (or at least break even) there would need to be criteria set up ... Everyone involved would have to get together ahead of time... A standard of quality -or- presetup table arrangements and let everyone handle their own banners/walls/displays... And scheduled events that would draw in crowds.
If there was one "Retail Store" for all the publishers present in a central location, thus freeing up the publishers themselves to do the demos, show product, etc and then let them go buy on their whims (or buy direct, too, of course) then it would need to be located in such a way people COULD browse. If anyone walked by upper deck this year, they saw lots of people playing games or watching movies, but you could hear crickets in the retail store. This most certainly wouldn't be acceptable.