Structural issues would be key to any proposed second floor expansion. That and the fact that Champlain Place is built on a marshy floodplain and perhaps the footings might not be deep enough to support the additional weight.
I have often fantasized about expanding the mall to the north and connecting it directly to Crystal Palace, but with the new Empire Theatre at Crystal Palace, this is likely no longer a viable consideration.
I think the mall is probably stuck at it's current size (at least in terms of footprint).
If a second floor expansion were ever to occur, I would start with the older section of the mall (between Wal Mart and Sears). I wonder if there is a business case for expansion? We always hear that there is a queue of retailers out there looking for space at Champlain, and mall occupancy is always at or near 100%, but is there enough demand to justify a second floor wing?
As much of a Moncton booster as I am, I rather doubt it.....