Blue
Ravenous Bugblatter Beast of Traal
I've fought in heavy armor back in the day in the SCA. While adjusting it is important, there's a lot more to that than wearing it effectively. Knowing how to take a blow on it, how you can move and not-move in it, etc. This would break my verisimilitude.
Looking at it strictly from a mechanical point of view, I can't see a party not having a heavy armor proficient character, so everyone will be able to wear it if enough exists. This makes DEX a bit less important, which is a good thing. Assuming PCs build around that (and since they grew up in that world so it is in character for them to do so) that's a lot more competition for magical heavy armor.
It dilutes the differences between the classes, and takes something special given to only a few classes and gives it to everyone, weakening them relative to the other classes.
Looking at it strictly from a mechanical point of view, I can't see a party not having a heavy armor proficient character, so everyone will be able to wear it if enough exists. This makes DEX a bit less important, which is a good thing. Assuming PCs build around that (and since they grew up in that world so it is in character for them to do so) that's a lot more competition for magical heavy armor.
It dilutes the differences between the classes, and takes something special given to only a few classes and gives it to everyone, weakening them relative to the other classes.