Having Str to define carry amount is logical and also pretty common in RPGs, so I don't really see any issue with that.
What makes it logical? You have magic spells in this game that can move objects and people around, so I don't see what's logical about having the weight limit depend only on a physical stat, thus forcing you to have a Strength based character in the party.
Talking about logic in a game of magic is nonsensical to begin with. You could easily have a system where weight is based on Int for mages, e.g. mages don't have to "carry" their items, but instead they somehow store them in some other-dimensional storage crate, or some such magical invention.
Pretty common in RPGs? Not a good argument. It's also common in most RPGs that mages cannot use Warfare type skills because those are meant for the Str based characters, which are always present in most of those other games. That's no longer true here - Warfare skills can scale on Str, Int, or Fin, depending on the weapon you are wielding, which is a step in the right direction. You can build a very strong party without any Str builds, but you will be at a disadvantage of the low weight limit. That's wrong. That's NOT logical.
