Well since you are a crab anyway - why not do it? It is about as close to any form of soldiering you will get in the RAF.
Actually I do not mind the RAF Regt at all. I would hate to have to spend my time guarding crabs. Did it for a bit in FI when I was inf and that was enough for me. So yes I do think the RAF Regt provides a vaulable function to both the RAF (it guards them) and the army (it stops the inf having to babysit the crabs). Thus I am also against the removal of GBAD from the RAF Regt as it means yet another task for the army to pick up, yet I so far have not seen an increase in the RA AD units to take on this task.
I spent 6 years in the Regt and they were very enjoyable. There are some bloody good soldiers in the Regt, proved by the fact that we picked up a gold medal on the Cambrian Patrol along with RM and Para regt. I left in 95 before they were stripped of the rapier role so I dont know too much about it now. Certainly the training I was given stood me in in good stead when I joined the TA as an officer. Like any unit there are those who don't meet the highest standards but some good guys. A couple actually did SAS selection and passed !! I saw lots of the world and it was great fun beating up the "guins" in the NAAFI !!!