Is it OK to have a class with just properties for refactoring purposes?

That is a great idea. It is typically how data contracts are done in WCF for example.

One advantage of this model is that if you add a new parameter, the consumer of the class doesn’t need to change just to add the parameter.

As David Heffernan mentions, it can help self document the code:

FrobRequest frobRequest = new FrobRequest
{
    FrobTarget = "Joe",
    Url = new Uri("http://example.com"),
    Count = 42,
};
FrobResult frobResult = Frob(frobRequest);