could be made for editor another kind of scheme:
example: a very basic line of units for the nations, this will liberate some needed space correct ?
as I am never try start mod, I not know the game engine limitations so not be angry about my lack of knowledge here
example: in editor: can have:

) USSR Ger Italy at least 1 allied nation include USA and GB units and japan... may be something else:
if there is a problem with number of different nations, this will correct but giving example:
german and italian units in 1 nation unit list
usa and gb in 1 nation unit list
and so on
this all in 1 scheme for editor. If number of different unit must be reduced, then for example only give enough different units to make ballance possible, in a more simple way but this will make possible more or less give pure nation
a more simple scheme list: 1 model of panzer 1, 1 model of panzer 2, 2 model of panzer 3, 2 model of panzer 4, 2 model of panther, 1 model of tiger etc.
same for russians and allied, limit the number of model for needed space if this is in fact the limitation (again, I not know about limitations)
but can be easier, I see for example a few foreign tank in 43-45 scheme for russian and german yes ? this easy give space for the more early units I refer before
but this is something to be think a lot about for exact selection of model etc. think about
peace