Choppabeef - you make some interesting points but I do draw you to the attention of Biggus's post about the process (qv IBNs, DINs, ad naseum).
I agree with your points about some very senior officers - and some aspirant VSOs (Wg Cdrs/Gp Capts) - who have been honing their chisels on Whetstones for years. JSCSC is one entry mechanism to this exclusive 'club' and some officers have made it to at least 1* without having done ACSC, but woe betide officers who have attened a foreign staff course - now that will be held against you.
Johnny Foreigners knowing about war? Utter tosh....