I don’t know about invading Spain/Portugal to get a European foothold… I thought it was a good idea at first, but then I considered a few other things…
First off, by getting a foothold you expose your troops to German preemptive strike. Where as if they are in Britain or on transports, this cannot happen.
Secondly, you lose your bombardment shots if you have battleships or cruisers. Those shots are often very tactically important in a battle where you don’t have a direct landline to push more troops in.
Thirdly, getting a foothold will not hurt the Germans at all. They suffer no economic loss and they can simply sit and wait for the Allies to attack France, or wherever. Since you can’t build an industrial complex (providing the territory is not worth anything), you can’t wage indefinite war there. And even if you could build an IC, if I were the German player, I would take you out and take it over before you could put guys there. God knows you could do that with Germany because their units will start so close to Spain/Portugal.
So… intersting idea, but I don’t know if it would be effective.