This is a terrible idea.
I live 40 minutes outside of Boston but sometimes I have meetings in downtown Boston. If I'm on time I'll park at the T (subway) station and take the T the rest of the way in but if I'm running late I'll usually drive directly in and park downtown. Sure it costs $20 for a couple hours but it is worth it when you are in a time crunch.
Making public transit the only way to get downtown is essentially saying you don't want people doing business in your downtown. Since taking public transit turns my 40 minute drive into two hours (each way).
Edit: of course I can park and take a taxi or Uber just like I can park and take the T but that adds a lot of time (and cost) to my trip. And that money is money I might spend at business downtown if I didn't just blow it on a taxi.