I'm not sure that there is any great need to do it. The Rnav approach is normally good enough, the Loc/Dme is available. Many aircraft have integrated approach navigation that turns these in to virtual ILS anyhow. The minima is higher than a cat 1 ILS but when the visibility is bad enough for it to be an issue then a switch to RW15 with a small tailwind is considered. I have done that a few times.
How many aircraft have failed to get in to BHX since the G/P became u/s? I don't know but I cant think it is that many.