I'm sorry, but this is the worst idea I have ever heard. I understand that with the construction going on, things have to be shifted around, but this isn't a solution.
My first concern is the weather. Rain being an obvious concern, but overly hot weather concerns me just as much. I can almost guarantee that someone will probably collapse from heat exhaustion, and a lot of people have issues that are made worse by the heat. My good friend (and usual A.A. buddy) gets HORRIBLY sick if exposed to heat and sunlight too long. Plus, if it's too hot outside, who's going to even come out to see the artist alley in the first place? Not to mention possible humidity damage to prints and other items for sale.
My second concern is security. I think we can all admit that Kumoricon takes place in a less than savory part of town, especially at night. I understand that opening the alley up to the general public might lead to a boost in sales, but what does con staff propose to do about any security risks? You can't remove someone who is acting up (for lack of a better term) from a convention that they're not attending. Would it be a matter where one would just have to wait for police? Also, hypothetically, what's to prevent someone from taking your spot in the alley?
I also have issues with artists being asked to tear down and set up their displays every single day of the convention. This is NOT an easy process for most!
Again, I'm really disappointed with this decision, and hope some sort of other arrangement can be made. I was REALLY hoping to apply for the A.A., but after seeing your announcement, I'm not sure that I will even attend the convention, much less apply.