The issue with Constitution is that from a game design standpoint constitution is basically benefiting the players twice over.
You could NEVER make a well designed character with just dex, or just str, or just intelligence and the way the other skills are designed.
Yet with constitution being the chief attribute governing Polymorph it becomes, to quote myself, "Too good". You would never need to put a single point into anything else creating an indestructible character who is the master of their craft.
The only way to balance such a thing would be to either
a) Make Polymorph terrible
b) Give the player sizable penalties (HP reduction for example) just for having Polymorph
To allow you to understand it...
Imagine a game where there was a character who actually got stronger the more defense you had. Where other characters are about balancing offense with defense or sacrificing one over the other... This one is all about having high defense means it has high offense with no downsides.
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But really it is the developers to decide that.
Can you at least agree that Strength is a better idea then Intelligence?
