Wi-Fi instead of NFC

[wifi]

Guys,

Please give me a suggestion on the following problem.

We are planning to install automatic roadway gates and stuck with payment solution. One of the ways to make payment must be based on smartphones. NFC and Bluetooth 4.0 interfaces are perfectly fit for this challenge and supposed to work in the following way: a driver comes to a gate, launches a special app (iOS and Android), touches a sensor on the gate by the smartphone, the gate system recognizes the smartphone by an ID and opens the gate. There is a problem here - not every model of modern smartphones has NFC and BT4.0 interfaces. As an alternative solution could be a Wi-Fi - we can install a micro wi-fi access point with THE SAME ID on EACH gate of the gates row. The power of each Wi-Fi access points shall be low to avoid collisions between gates and their false response.

So questions:
1) what drawbacks does this solution can have and ways to overcome them?
2) to decrease the initialization time between a smartphone and a micro wi-fi network (ideally it shall be 3-5 sec.) is it possible to use the following solution: install a "big" wi-fi network that covers all gates in the row to make drivers' phones "catch" the wi-fi network in advance (e.g. waiting in a queue of cars) and then make a kind of handover to a micro wi-fi network of a particular gate when the phone within its field?
3) what wi-fi chip can you recommend to use for the design of the micro wi-fi network?
4) maybe some other idea "how smartphone can manage a particular gate" pops-up in your mind?

Thanks in advance for your ideas!