Yes, each of the 4 Blocks moves and attacks with all units at once. As for control of tt, perhaps in future WWII versions will borrow the rule from 1914 that you always have to have one infantry to make an attack, and leave one as a last unit after all other units types have been eliminated.
Alliances between blocks should be strictly limited, for example the “Soviet Block” would not permit Western Allied units on its territory or vice versa; the Axis and Japan would be similarly restricted. There have to be some benefits to being allies however, such as sharing sea zones, and being permitted to fly over an ally’s tt - but not land there.
Moreover, some scenarios would not begin with historical alliances in place, for example a pre-1941 scenario would not have the Axis and the USSR at war.
Include an “open” scenario allowing each of the 4 players to make alliances as they see fit; certainly the Reds and Japanese would have a pact - each cannot attack the other until their respective main enemy has been defeated.
It would make sense for each block’s pieces to all be similar in colour, so dark green for US & light green for British Empire, maybe a green-brown for France, turquoise for Chinese?
Germany in dark grey, Italy in light grey.