I believe the Merlin had an organic CSAR capability briefly when it first stood
It was round about 2005/6 IIRC. I remember a couple of US CSAR / PJ types coming to the sqn to oversee a validation exercise which occupied a lot of the Sqn's time. The exercise went as well as could be expected and the sqn passed and as such the UK was declared to have a 'JPR capability'.
Pretty much the next day the capability was put in to abeyance and hasn't to my knowledge been seen since for all the reasons discussed already.