The law would not prevent users to stick with Apple Pay if they so wish.
If banks choose not to participate in Apple Pay should the government force them to do so? Should the government also decide all the rates so that a bank cannot try to charge too much and thereby prevent Apple for signing a deal? Or is this concern only one way, against Apple (the company with among the highest customer satisfaction ratings) and in favor of the banks (companies with about the lowest customer satisfaction ratings?
This would only be an issue if payment terminals start to discriminate applications, e.g. blocking some apps or only accepting others, "forcing" users to forfeit this or that app to pay at this or that merchant. The EU has already on its agenda to make such arbitrary limitations illegal though, since they intend NFC payments to be standard.
That is just one problem. If Apple was required to allow Chase access to their device, what incentive do they have to also participate in Apple Pay?
Furthermore, what if the "one app" sucks or is limited compared to what competitors offer, or has different features? It's s true that choice is a double-edged sword, but so is lack of choice.
You keep talking about “lack of choice”, but what you mean is that you want the government to make user experience, security and development choices for the companies building these products. I am not sure what you think, but I think Apple does a much better job of that the TSA app or my local DMV.