I actualy kinda enjoy that in Ox or a Bear shape im able to carry almost tripple amount of stuff back to vendor, especialy after some big fights ... since i dumped Strength ...
But i would totally agree that Cat (and possibly raven, didnt try that so far) need some adjustments. :-/
Again, I want to stress that this change could be made without reducing the benefits to these higher strength forms. As said above, Shapeshifting either melds your gear into your new form OR "is worn by it." Therefore, it would be reasonable to assume that when shapeshifting into a low Stre form, you would choose the meld option (so your new Stre would not change your carrying capacity), and when shifting into a high Stre form, you choose for your gear to be worn by it, and therefore your carry capacity is still increased in that form. The only question is whether Larian could effectively implement it that way.
By RAW (not that it would need to follow this, necessarily), your gear doesn't change shape to fit you if you choose to wear it instead of having it absorbed and the DM can rule that it just falls to the ground. It's a little difficult to argue that armor that fits a humanoid would also work for a cat or a polar bear. I could potentially see some magic items work through a transformation (e.g. if you had a magic earring or something, then the piercing could stay consistent through the transformation - it doesn't rely on the size of the creature).
In my mind, the most realistic (and simple/consistent) thing is to have all equipment be absorbed (making inventory inaccessible and not contribute to carried weight, so low STR wouldn't be a problem) and provide no benefits while transformed. Shifted druids would use their own mental ability scores and everything else would come from the shape they've assumed. And then adjust the creatures that you can wild shape into to be balanced and satisfying to use.
I see what you are saying, but I was actually thinking more about equipment, rather than worn gear. The exact quote from PHB was:
"Wild Shape: You choose whether your Equipment falls to the ground in your space, merges into your new form, or is worn by it"
So maybe this would not apply to worn gear and such, that would be required to merge, but I figured the "worn by it" option would be the equivalent of placing a backpack on the larger animal (even if that would look kinda ridiculous in practice, it's technically doable lol).
I really just see this as the easiest way to build consensus for allowing lower Stre forms to keep their caster carrying capacity (because otherwise these forms can't really be used due to auto-encumbrance), without having all the people worried about losing their polar bear perks oppose the idea.
