They should consider building up like the rest of the area; add a couple of office towers attached right to the building to make Square One a more mixed-use development. Maybe throw a hotel in too.
This whole area needs to be 100% redevelop and I would do this.
Phase 1:
Stage 1: Remove all surface parking north of Walmart to Sq One Dr and east of Sears with 5 levels of underground parking that will reach street grade next to the current loading dock entrance. A new loading dock area to be built to replace the current Walmart one as well the new expansion.
Stage 2: A new 4 level mall be built on top of this new underground parking structure with 6m minimum ceiling height. A new food court to replace the current one and be larger. The north east corner would see the relocation of the current Sears or what it may come in the future. Sq One Drive will be reduce to a single lane in Phase 2, but all building face along Sq One Dr will have 6m sidewalk with entrance to the retail. Whole Food and pads will be relocated to this new expansion. The expansion will go over Walmart to the point you have a 30-50's office tower above it as well the north east corner. The roof area would be a green park area between the 2 towers. Rest of the roof area would see 8 floors of residential on top of the mall. The mall walkway will have large skylight over them. There would be an out door skating rink on the roof.
Phase 3: Once Whole Food and the pads are relocated to Phase 1, that area will see another 4 level mall expansion including underground parking as Phase 1 with 100% glass walkway over Sq One Dr that includes the floors. The east side of this expansion will see the building of a new Transit Hub on various levels to meet the ridership needs of 125,000 riders daily. On top of the north east corner will see a sloping hotel/office/condo with a height of 100 floors with an observation tower at the top. The mall roof will see more green park space.
Phase 4: The current transit terminal would be remove to allow Station Gates to connect to Square One Dr. This block would see 2 k-12 schools holding 12,000 kids as well a community centre with an Olympia swimming pool, 2 hockey pads with one being Olympia as well a number of gyms. This would be the recreation site to house a pool hall, 5-10 pin bowling and so on. Again 4-8 floors of residential on top of it.
Phase 5: This would see the removal of the existing Sears store and the north mall area between Sears and Target. The existing road off Rathburn would be extended south with provision to connect to Burnhamthorpe Rd under Phase 6. The same thing will happen here as in Phase 1 with provision to go south in Phase 6. A new Target store will be built in this phase as well another anchor store or 2.
Phase 6: Rest of the existing mall will be torn down and replace with the new extension as Phase 1. This will include the existing parking structures and the relocation of the Bay. This will be the last expansion for the mall as well seeing the 2 north-south streets connecting to City Centre Dr. There would be provision for taller office and condo towers in this phase.
Phase 7: This Phase is in the north-west corner that would house Movie Theaters, bars, entertainment, hotel, convention centre, higher condo towers and etc. A few churches can be added to this area or other phases.
Rathburn Rd would see a transit corridor on the south side to service the area as well the new Transit Hub. A single lane with bike lanes as well wide sidewalks will replace what there now. City Centre Dr on the east side will see the same thing with transit being on the west side of the road with LRT in it. The centre platform will run the full block.
Phase 8, 9 Will take up the rest of the current block with residential ranging from 6-60's with 30% parking space for them.
Phase 10: Would see the current pads by Hurontario St replace by Residential and office with 30% or less in parking space. A new fire station would be built there also.
Phase 11: Would see the existing area for the movie theater replace with a sport field for everyone as well a park, playground for kids, even though the roof of the mall will have some on them.
Phase 12: This would see the lands on the north side of Burnhamthorpe being redevelop 100% with new north-south street going through them and all existing towers being replace with street edge tall towers with retail at grade. Again, parking would be at 30% with the sidewalk pedestrian friendly. It can also be a mix area.