Instead of the Toronto, you could try Mississauga. Mississauga, a 1 hour drive from Toronto, doesn't have any airsoft field, arena, or shop. You will get practically no competition, plus the fees for running the business will be cheaper than Toronto.
One innovative idea regarding airsoft facilities would be the merger of airsoft with parkour. Although the effectiveness of using parkour for dodging is questionable, getting from point A to point B with it is not. Instead of an outdoor field, you should focus on an urban setting that offers a more varied game play. From my experience from First Person Shooter games, the most popular maps are not ones with a big area. Rather, it is the complexity of the map that wins the hearts of those players. Maps that have 3-4 levels, for example a basement, ground floor, 1st, and 2nd floor, with many stairs, elevators, ladders offer a level of variation in gameplay unprecedented by any "plain old field". More importantly, those who are familiar with parkour can better take advantage of the urban environment.
An outdoor field is not without its merit however. In an outdoor environment, good use of camouflage is an integral part for a teams success. Weather can change, turning a forested area into a mud field or a blizzard making advance difficult. Therefore, I propose an airsoft arena that combines the two, enabling situations that place an assault team attacking from the outside, and a defending team inside. If someone from assault wore a ghillie suit, it will now work against him in the building; if a person from the defending team ventures out into the fields, he might find his load-out inadequate for the environment. If indoors and outdoors were to be combined, the map wouldn't even have to be big. Undoubtedly, the size of one football field would suffice. In the end, its not how many acres the place is, its how you utilize it that's important.
By the way, living in Mississauga, I heard a landlord is planning on selling/renting a piece of his land. A small private school across the street from that field is on his property. But when the principal expressed her desires to move the school to another location, the landlord tried to persuade her by giving her part of the field for sports related activities as well. However, after a many years, nothing have been done with the field for reasons unknown to me. If you are seriously considering opening an airsoft arena in Mississauga, I strongly recommend you to look into it. There are many advantages to this particular field. Next to a mainly Chinese oriented shopping plaza that brings in thousands of people per week (the parking lot is packed on weekends), it is unquestionable that it is a location where most people in Mississauga will know of your business. Plus, since most Chinese are already familiar with airsoft (they call it "war game" in Southern China and is a popular recreation) most of them wouldn't mind spending their weekends in such as fashion.
p.s. I am new to this forum, and this is my first post. Although I have never scrimmaged before and my knowledge about airsoft being limited to what I read (and I do read a lot) and the guns that I have fired, my knowledge with the area is not. So if you have any questions, feel free to ask. If there was an airsoft arena in Mississauga already, I would've undoubtedly invested piles of money on airsoft already.
Cheers