The Huskies stadium site is very tight. Not only is the site tight, but the number of rows in Molson Stadium would necessitate that the upper rows tower high over The Tower on one side and meet Loyola residence perhaps as many as 10 floors up on the other. Neither result is appealing.
There are things one can do to fit a 20,000 seat stadium there though. Start the upper rows of seating at the roof height of The Tower, then continue down till you get about 7,000 seats. This would mean lowering the field quite a bit from where it lies now.
Building back up the other side with another stand of equal size would create a stadium of about 14,000. Using this design and capacity on each side, you avoid towering over the athletic centre or abutting up to Loyola.
Where to put the additional 6,000 seats? 3,000 at each end. Having lowered the field, there's room to add these end zone seats without causing too many issues with the buildings at the north and south end zones.
You might want to use Ron Joyce stadium as a template. It's much easier to use than Molson. Their is no athletics track, and just one grand stand seating 6,000. It's easier to cut and paste another stand on the other side to get a 12,000 seater. If there is enough room, you could easily add more seats to either side, play around with it a bit, and estimate what the largest capacity you could fit at Huskies Stadium without end zone seats. Here's MAC's new football stadium:
Ron Joyce Stadium
http://www.cpci.ca/images.asp?month=82008&image=1.jpg
It's quite easy to see that if MAC built that stand all the way around, they'd have a stadium with a capacity of about 6,000+6,000+3,000+3,000=18,000. (The end zone stand would be roughly half the size of the grand stand.) Ron Joyce cost $43 million and was built in 2008.