I would worry about the traffic problems a 20,000 seat venue would bring. Hwy 7 during rush hour (or Saturday afternoon) is a nightmare. Warden and Kennedy are busy. The downtown Markham development has got office and residential, and to plop down the equivalent of the ACC without the equivalent public transit? The Stouffville GO train and VIVA bus system are in no way equivalent to the GO/TTC options out of Union Stn; besides which there is no GO train service and virtually no bus service late at night when most events would let out. How would someone from Toronto (much lesss Mississagua) get home from Markham at 11 pm without a car? You can't even find a taxi to take. Meaning: everybody will be driving and you'll need an acre of parking and some kind of traffic control system. Has anyone seen people race from their cars after exiting a GO train because they know there will be a traffic jam exiting the parking lot? How about 20,000 people in their cars exiting a Markham arena at once?
As a Markham resident, I'm not saying I don't want the arena at all (although I would prefer Richmond Hill or Vaughan). But if it's going to happen there needs to be much planning on how the traffic is going to move in and out. 'Cause, frankly, driving in Markham is worse than driving in downtown Toronto.