I have no idea to be honest and a quick Google search wasn’t helpful... My assumptions are just based on pics that have been posted of the house under construction and of the limited pics of the proposed location. House designer Peter Faragher has said that the current house layout was designed to accommodate a smaller footprint.How big is the Canadian studio that is home to the house Kingston? I know the US one is about 15,000 square feet, which includes the house, studio and production offices. The Canadian studio is in a different studio to the house, but their house also includes the backyard, so require pretty much the same space.
I think from the two reported studios considering roughly 485m2 is 5000 square feet it would need the bigger venue to accomodate the house, though as you say if they lose the camera runs that frees quite a lot of space. Much depends on whether they can use any outside space too - and with it being pre-recorded I wouldn't be surprised if any challenge arena isn't necessarily directly linked to the house and they are guided to it by producers, just like in Survivor how they are driven to challenges and tribal council.
For what it’s worth they really should just copy the BBCAN house with some minor adjustments to accommodate a proper outdoor area. They could easily keep BBCAN’s annex in place for competitions and make room for a proper backyard off the side of the building.