The problem is more about getting the Rawlsian view accepted as correct than about whether or not it's a valid ethical system.

The issue is that it does nothing to solve inequality unless it's a narrative that everyone grows up with and which is somehow built into policy.

How likely is it that it could be installed in that way?

Without political guns and butter it's just an interesting idea. I can understand the appeal because it has a certain neatness to it, but I think it makes one significant mistake, which is to assume that given a rational choice, everyone will decide that inequality is bad.

I don't think this is true. The reality seems to be more that a small minority of the population believe that inequality is a good and excellent thing, and can't get enough of it - without limit. If they were the ones owning 99% of the resources and everyone else was starving they not only wouldn't care, they'd celebrate. And they'd want even more.

Without those people collective decisions would be far more intelligent. So any useful ethical system has to be able to deal with them firmly and realistically.

So I think you can use Rawls in debates with reasonable people, but not as a tool to persuade the unreasonable ones.