With all due respect, I think you might be underestimating the effects. Looking at the screenshot at hand - I am aware the numbers might change - 50% manpower increase in the early game are huge! Especially if the nation that won this war doesn't get it. This mechanic can lead to the wierd situation that by the time the truce is done, the nation that got trashed in the war will be back up to snuff, while the nation that won (maybe hard-earned, by spending all of its manpower) will still be recovering.
That's very silly. Losing a war does not make your nation stronger. If you guys want to fix the Blood-In-The-Water-Calls-For-Sharks-Effect that sometimes gets nations like France killed in multiple wars, then tweak the AI's peace-deal behaviour. Currently the AI is programmed to fight to the last man, since it will not accept peace deals higher than the current war score, even when being drastically out-numbered, out-teched or out-classed. A player in such a nation would cut their losses and accept and unfavourable peace instead of tanking their economy - pretty much what you want to save the AI from.
So yeah, polishing up on that AI would be the smarter design, instead of just slapping a fat, ahistorical modifier onto things.