Newt,
I completely disagree.
You may be referring to bygone days and practises but I'm not. Today's VSOs and those in the pipeline to replace them are indeed made up of the various branches (the majority are NOT pilots!) and almost all of those that spring to my mind have a great deal of experience of ops ("Front End"), having commanded at either/or both the tactical or operational levels. Few serving members of the Armed Forces, across all ranks, will have avoided the last 25 years we've been fighting baddies in the sandpit!
You say pilots should be professional pilots? The vast majority of pilots don't actually make it to VSO rank (1*+). Career routes such as the Professional Aviator spine allow pilots to remain in flying or flying-related posts for their entire careers. Indeed, a healthy, modern Air Force depends upon such people to pass hard-won experience onto others. For the very tiny minority who's personal choice and capabilities suit promotion to high rank then so be it, but it's their choice. If you are referring to VSO posts being filled "only by pilots" then you're out of date; take a look at ACAS (an Engineer) and the 2/3-star non-pilots across DE&S, DIO and in MoD. Those individuals are where they are by their own merits and demonstrate a far more level playing field than you've implied.