It seems Spain is an absolute must for the Axis player. It's quite easy to get Spain join relatively early if both Italy and Germany invest full chits on her. The Spanish navy is very useful in the Atlantic and I even put the Spanish HQ + 2 Armies, AF and the Panzer to good use in Russia. You could also attack Iran (after Iraq joins) with a combined Italo-Spanish force and head north to the Caucasus from there!