Allies:
There will be late war items even mixed in with some British units. The Allies will not be as advanced but still have late war units, jets, late war tank such as a Centurion possibly.
Japan:
You are correct that the Japanese did not develop the weaponry near as much as Germany, but you did see the Shinden jet we have unveiled. The Shinden was developed with a flying prototype by the end of the war but with a prop, the jet engine was not finished. There will be some late war units and you will see either the G10N or Ki-97 Bomber as well as late war tanks.
Germany:
The sky is the limit here. We have already shown the Ho XVIIIB2 Bomber on our facebook page. We are assuming that the Germans want a proven tank as easy to fix during the Invasion, you could see some E Series tanks and several vehicles based on the Panther Chassis.
German jet will be more advanced than the Me-262.
All Soldiers will be like Greman Grenadier, SNLF Japanese Marine, and a Special unite Allied Unit.
All units will have SP Artillery and SP Anti-Air Units, of course…late war.
Hope this helps.