Proposals concerning the badboy:
1. A high BB should be a legitimate casus belli,
so there is no loss of prestige, if you attack such a high-BB-country.
2. you should be able to claim provinces for allies in a peace deal,
but also for non allies or not yet independent nations.
e.g.: Britain has beaten Russia badly, but does not have any intererests in their provinces.
So they could claim Finnish provinces of Russia for Finnland
and then Finnland will become independent.
That way you could harm your enemy without getting a huge BB.
So if you claim a province for an ally,or a sattelite you get BB,
but not as much, as you would get if you claim it for your own.
If you claim a province for a neutral country, or to
free a country, you get no BB.
3.the BB you get should be linked to the impotance of the povince you get, also
you should get less BB for colonial povinces and more BB for claiming core provinces
from your enemy.
4. Finally, less BB if you didn´t start the war. Like Poland after WW2 received
one fifth of Germany without beeing concidered as an agressive country.
It was perceived as a fair punishment of Germany beacause they started the war.