I might be wrong but the 'comfort letters' that appeared to grant immunity to suspects were deemed illegal so anyone caught could still face prosecution for their crimes. The other aspect relates to convicted terrorists being freed from prison as part of the agreement. In other words, those...
It may well be that it wasn't on the table because the powers that be at the time didn't consider that any of those in service would have committed a crime. However, had an immunity been in place it would have served to have drawn a line under the period of the troubles. As it is, we now have...
Isn't the point that whilst everyone pretty much appreciates the job servicemen do, there is a standard that we expect of them. We don't want to see them lower their standards to that of the common denominator. If fighting Isis for example, we don't expect our troops to behead any prisoners...