I've been developing a philosophy in regards to this, I have these checks to make:
The province is the domain of a relatively important state in the region that was independent during the time period.
The province was heavily contested in numerous inheritances, wars, and/or treaties, and exchanged hands numerous times seperately from the province it is currently lumped into AND contains at least one city, fortress or port of significance.
The province is historically an independent jurisdiction and has NEVER EVER been a part of the province it is currently lumped into. This only works if it can't be lumped into another province instead.
The province contains a very important seaport and shipyard, but the province it is lumped into already has one.
The province contains vastly different terrain from the one it is lumped into and is significantly large.
The province has a totally different religious or ethnic makeup than the one it is lumped into, and it is significant to history that this is represented accurately.
A state had significant territory in the area that is not represented at all.
The province is the domain of a relatively important state in the region that was independent during the time period.
The province was heavily contested in numerous inheritances, wars, and/or treaties, and exchanged hands numerous times seperately from the province it is currently lumped into AND contains at least one city, fortress or port of significance.
The province is historically an independent jurisdiction and has NEVER EVER been a part of the province it is currently lumped into. This only works if it can't be lumped into another province instead.
The province contains a very important seaport and shipyard, but the province it is lumped into already has one.
The province contains vastly different terrain from the one it is lumped into and is significantly large.
The province has a totally different religious or ethnic makeup than the one it is lumped into, and it is significant to history that this is represented accurately.
A state had significant territory in the area that is not represented at all.