Well... IMO, an R Grade will always be an R Grade, however good as it may be as near to 4.5 grade, or as bad as 3 or below grades. And usually, their interior and exterior grades are also quite low, like C, D, E, etc.
If you can very well understand the auction sheet, and can fully know which things need repairing or replacement and can manage it accordingly, then for sure, you can go for it. But... Buy an R Grade car, at the price of R Grade, at right price, and not at the price of 4 grade or above!
Usually, problems, worries and headaches start when you buy an R Grade car, at the price of 4 Grade or above. Of course, provided auction sheet by the showroom or importer is fake.