They do not have build exactly what's proposed as long as such requirements presrcibed in the by-law are satisfied such as max. height and density, etc. Since a site plan application has not been approved yet the floor layouts can change to accomodate different size units. However, if that is done and you have more 3 bedroom and bachelor units and less 1 and 2 bedroom units, then that changes the amount of parking required based on the formula in the zoning by-law (and outlined in the staff report). If the change in unit types results in less (or more) parking spaces required, then a minor variance application may be required.
Changes can be made but the more changes that are made whether they are big or small only adds to the total costs of the development. The increase in these 'soft' costs can be small or large and depending on how much extra it works out to be may not be worth it if they are expecting a minimum return on their investment. They could still make the changes and meet their expected return, but that would mean more $/sf since the overall GFA hasn't changed. Of course construction costs may come down and fewer units would require less appliances and balance it out, granted soft costs are significantly less than hard (construction) costs.
So basically, some changes can be made, but the feasibility analysis was (probably) done well before the application was submitted where they would have looked at various options with different number and types of units. But given they are sitting on this for now, they might decide to adjust their analysis based on changing market conditions.
