Unless you fancy a non-aircrew type stumbling about in an aircrew specialised post, which is exactly why the Wg Cdr branch no longer has "GD Any" monicker attached to it.
s'funny. Another view is that it was all a bit difficult finding out the non-aircrew types were actually very capable and doing better in some previously aircrew posts and it was upsetting the order of things. So we revert to job protection to ensure survival of the species.