I think the Commonwealth population is very large but not excessively large. More like the upper limit It is more the mention that other great powers are short on population which is simply not true for its time period. 

I personally think that the Commonwealths army is too large for the time period. There is simply not a single point in 19th century history where any of the worlds great powers managed to field an army of over 1 million men during times of war. Not to mention that very large numbers of soldiers in the field proved to be unsustainable from both a financial as a supply point of view. The most important causes of death in war during the 19th century where starvation and desease, not actual combat. Also most great European powers struggled with the financial burdons of large standing armies.

I personally think that a high amount of points in Martial prowes should account more towards actual combat performance, leadership and quality of equipment rather then size.