I agree. I was there when Moss Park opened and it had 1 wet and 1 dry canteen for us junior ranks and a total of 8 messes for the officers and Snr NCOs upstairs. Meanwhile downstairs were 4 office suites, one each for each battalion/regiment and two lecture rooms.
Moss Park is actually an example of poor planning in that it has limited space available for the parking of both military and civilian vehicles. It might have been adequate in my day in the 1960s when everyone took the TTC to get there but these days ... There is very little expansion capability other than to build a wall along the west and north side to allow more parking space, and to negotiate additional land to the east which I presume is a non starter due to the recreational facilities there. It would have been easier in my day when all that land was empty except for the residents of the neighbouring mission wandering around.
More than that, however, is that a battalion, even one with 1 full-time and three part-time subunits (or for that matter even separate sub-unit in its own armouries, needs a fair bit of footprint for stores, vehicles, maintenance, etc. Even if some of the vehicle storage and maintenance can be shuffled off site. Most of these armouries were designed for very light scales and are hard to reconfigure or expand and there are some things that you need to function efficiently. For example clothing stores. A properly functioning 30/70 battalion, IMHO, should be able to do everything from recruit processing to basic kitting in house. I think getting people from "Hi, I'm interested in joining" to having their butt in a lecture room chair wearing the right gear and learning how to use their rifle should happen in weeks, if not days, regardless of whether they are joining the RegF or ARes component of the battalion.
I personally prefer the idea of buying up a derelict shopping centres in urban areas for their usable acreage.