I've seen this idea tossed around by a few people, and there are few models available for success. Not speaking from experience but from observation, an indoor facility in Ontario will either need to have other uses during airsoft down time to make up the bulk of its revenue, or else cater to airsoft players only as a secondary market (i.e. full-time training facility for LE, mil, etc.) Players are a fickle and cheap lot, especially on this forum.
There are those willing to pay for memberships, be they monthly or annually, but these are very much in the minority.