One stat to rule them all, or what if we merged Dex and Str?

[Segev]

I can think of several explanations. I believe the easiest one is "she could do it before, she just didn't know it, having never tried; after all, she had a pretty developed musculature, being able to do back flips and all that sort of things. Add to that the adrenaline of the moment, and it's perfectly understandable".

Sure. For some. But all?

Well, regardless, if they're trying the checks, they are going to succeed at them.

And that's the problem.

This is the point of this thought experiment. To check whether this is true; or, to be more precise, whether they can be represented by other mechanics than the ability score. Perhaps you can just represent them by giving the "strong guy" Athletics, Heavy Armor, and a Maul and the "nimble guy" Acrobatics, Light Armor and a Rapier? Just not having proficiency in Athletics (if you want your character to be more nimble than strong) will go a long way.

Technically, you could remove ability scores entirely and use other mechanics to represent what they do. Ability scores do two major things: 1) They provide an insight into The Character in terms of what their raw capabilities are, independent of personality or specialized training or unique skills. Whether this is valuable or not is an open question, I think. 2) They provide a fallback/default place to look to answer the question, "Can you do X?" when there isn't a feat, feature, or spell that definitively says you can. They provide a varied base for resolution of capability that is lost if you have only a level-based bonus (or no bonus at all and just roll a die/flip a coin).

I think (2) is too valuable to give up by getting rid of attributes entirely. I think we should be very cautious about merging or adding attributes unless you have a statement about the game and people in it you want to make. L5R uses its "rings" and their associated mental and physical attributes to make a statement about the metaphysics of the setting. White Wolf wanted more granularity, and eventually codified 3 attributes per major category of physical, social, and mental (though they didn't do the best job, in my mind, with social, since whether Charisma or Manipulation is called for is entirely in the stunt you pull to do the action, which isn't a good delineation in my mind). BESM went for 3 stats, Body/Mind/Soul, and then notably has defects for Body that let you split out being weaker at strength based stuff or dex based stuff.

I don't know about your sheets, but I believe the official sheets don't even have a "maximum encumbrance" field.

No, but they have a space for "Strength" and the rules for how much you can carry are in the PHB, and are based on STrength. Merge Str and Dex and now you have anybody who is agile being able to carry a lot of weight.

And I think it's pretty bad form to tell other players what their characters can do (unless they are newbies, and even then it'd be polite to wait for them to ask for your help). Specially if, the way a character is described, the other characters would have no idea that she's actually capable of doing that stuff.

Perhaps not, but it is also rude to deliberately make a character that holds back the party.

It's one thing if you're trading off things, but if all you're doing is deciding, "Nah, my PC failed that save vs. being used against the party despite having a bonus that actually would mean the d20 roll succeeded," is kind-of rude, too.