On Turn orders and DOWs.
A very old House rule is the All Axis turn, then the All Allies turn. So basically Germany, Italy and Japan purchase units, combat move, resolve combat, non combat move and place units at the same time. Then all Allies do the same. Now this is a real time saver, and it only take away the dead time when 7 players are waiting bored for one player to do his stuff. But it will affect the tactics, since some players like to exploit the gamey stuff like can openers or reinforce a newly captured territory with other nations fighters. But besides that, the All Axis All Allies turn is very good.
Now since some players start as neutrals, I suggest this
All Axis turn
All Allies turn
All Neutrals turn
While not at war, neutral USA and USSR must purchase units and do non combat movement in the All Neutrals turn. After they have been attacked, they move to the All Allies turn for the rest of the game.
I think all neutrals should be attackable, even the true ones. But Spain, Turkey and Sweden should be cut in several territories, not just a big one. So if Germany attack Western Turkey, then the other parts of Turkey join the All Allies turn. It would be too bad if vital areas and great war contributes like Spain, Turkey and Sweden was impassable just because of simplicity.