This system, more than it's totally implausible, makes you LOWER your miliatry slider if you want a big army. I think that the Precentage system in HOI3 is much better in this case.
Didn't most officers in a good chunk of this time period buy their commissions, making it not totally implausible?
Only a miniscule number of soldiers promote to officers anyway, that promotion path doesn't really affect the size of your army. It's negligible compared to the amonunt of promotion and demotion of soldiers to other classes if you raise/lower military spending.makes you LOWER your miliatry slider if you want a big army.