I suspect the problem would be the mast 587'AMSL at around 2 miles on the centre-line which would, I'm sure, infringe the protected area. (NB I am at home and looking at a chart which is not current, so the mast may not in fact be there now).The hills would not pose an obstacle problem for an ILS approach. It is probably down to money! I would suggest that the mast would need to be changed (lowered/moved) to allow an ILS but I'm sure an ILS expert will answer in detail. Perhaps someone can confirm the mast is still there?