I can see where they are coming from. You only need to look at the existing ex service MPs in comparison to the career politicians. I have been quite impressed with Stephen Barclay not my MP but he does a sterling job on the PAC and is a good constituency MP. I am sure there are others. Ashdown for instance.
Now for the Civil Servant: I think there is one Rory Stewart did a great job with the Diplomatic Corps in Iraq after he left the Army.
DN - I empathise with you about the CS. I think the negative side you speak of was prevalent in the MoD. Sir Gus tried to change things. I certainly wish I had come under his influence earlier. There was a definite attempt to isolate us MoD Civil Servants from the rest of the CS. I left the same day he did for many of the reasons you describe. I treasure the hand written note Sir Gus wrote me on his way back from the Far East with Dave.