That kind of defeats the purpose of removing the parking requirements. If you require every 3 units to have one parking spot, you raise the price of each unit by 30%. Additionally since tenants are paying for the spot anyway, it incentivizes them to buy a car that they might otherwise do without. If there turns out to be a market need for parking spots, I'm sure someone will step in and build a long term parking garage in the neighbourhood, but you aren't mandating every tenant regardless of car ownership desire subsidize the others.