Assuming you open your cafe on a viable commuter path, you can take advantage of this subsidy and your economics can work out. You can improve your economics even further with the tactics a lot of cafes already to nudge behavior at the margin, some of which you've already noticed (e.g., less-than-stellar wifi, thermostat at slightly cold temperature, limited actual seating space, only 1-2 customer-accessible wall sockets, etc.).
On the question of charging-by-the-minute: the marginal profit you can earn on coffee is higher than marginal profit you can earn on real estate. That's why Starbucks (which sells coffee and gives away real estate) is a better business than WeWork (which sells real estate and gives away coffee). Therefore instead of charging by the minute, you might consider raising your coffee prices and/or controlling the average amount of real estate you're giving away per unit of coffee sold.