I think they're going about this the wrong way.
The plaza is a great asset to an area that's about to be filled with retail, office space, and apartments in Centennial Yards.
The problem with the plaza is that it has no shade. That's the reason nobody uses it. Removing the existing towers and putting in their place canopies that open during sunlight hours— like these, in Medina, Saudi Arabia of all places— would turn a dead plaza into a great place to picnic.
Reddit Link
The solution to their retail problem lies with the orange deck, at left. Retail can be built atop the deck, facing the plaza. The gap between the deck and the plaza can be capped to allow access.
They can also add additional retail to the deck expansion. If they model the new part of the deck after the parking podiums in midtown, they can put retail along the ground floor, facing the Home Depot Backyard tailgating site. Above the retail, they can shield the deck with an LED signboard, adding another source of revenue. If they wanted to go hogwild, they could build a new tower atop the deck expansion, maybe for office space for GWCC staff, Stadium staff, a media center for sportcasters, or another hotel or apartment building.
Another way they could expand retail options is by extending both Andrew Young International Boulevard, and the adjacent pedestrian plaza to the north, westward to Northside Drive. This connection will require a ramp structure downwards to the ground level. The south side of the ramp will, like the deck expansion, face the Home Depot Backyard, where a row of retail space can be added.
Alll the new retail I mentioned can be serviced from Mangum Street, below the plaza. The site as configured in the image means delivery vans, trash/waste trucks, and other service vehicles will be competing for space with other drivers and pedestrians. The service areas will also be visable from the plaza; not an ideal situation.
Finally, directly south of the Bus Terminal, there's a huge hole still left where the freight rail line runs under. It's right next to the MARTA entrance, and it's a fall hazard. They need to cap it and add a cylindrical vent, and find a local artist to make it look like it's *not* a vent.