Had St. Peters not been located where it was, I suspect it would have been demolished and the site re-used. The location probably spared it from that fate, but... left it to the vandals over the years.
Security???? Reducing Vandalism??? Have you been there?
Naive? I did say try. Bar installing a 24/7 security patrol, there's little could be done at anything approching a reasonable cost other than fence the area off. To steal someone else's line, the vandals only have to get lucky occasionally over the years to do their stuff.
Having seen the documentaries on the construction of the building, I was using the terms restore and preserve in 'National Trust' terms, which is probably more like controlled decay, without the help of vandals. If you're familiar with sites like Spadeadam, then that's more like what I had on mind.
In modern or re-use terms, I think the remaining structure is a non-starter, and plans based on that thinking will be unlikely to get anywhere. Better to be realistic and aim for retention of what has survived so far. This view may not be popular, but it would be better than spending another 30 years aiming for better while nothing was done.
Incidentally, Google maps have hi-res pics of the area, if I'm not mistaken it can be seen clearly NNW of the golf course.