Experience and morale

[Imp]

Its never going to be right its just a BASE. Different situations would effect the overall morale.

I think the Japanese already get some sort of hidden morale bonus. Been a while since I played them but they seem to bounce straight back after taking punishment.

Also while some formation modifiers are uniform like scouts not all are.
Units like Paratroopers get different modifiers based on the OOB they are in.

The only problem for me is actually early Russia. This is because below 60 they react poorly & their opponents are above average for that time period. So you are talking a difference of 20. Takes a bit of time to adjust to fighting with them because of that difference. Makes it challenging as things are far more likely to go wrong till you realise you need to expect that.