Terath Ninir
Yog Sothoth loves you
I'm a 3e/Pathfinder fan, but one thing I've always found a tad ridiculous as stat bloat. Oh, the mental stats aren't too insane, usually, but it's not unusual to see a monster with a 30, 40, or even 50+ Strength score.
My suggestion for 5e is: don't do this. Size should have an effect, but not directly on the stats. Especially if skills default directly off of ability scores. If a monster is going to make a Con save against your attack (or whatever the exact mechanic), it's really going to suck if they have a 30 score and you're a fighter with a 16 strength.
But size should affect things like your damage and your hit points, right? Right! But just do it directly. If you're large, you use bigger weapons and get, say, a +2 damage bonus. You get bonus hp per HD, or maybe even just a flat +10 HP bonus. You can still have a large creature with a 3 Str or an 18 Str -- but they can do feats of strength that a smaller creature can't. Similarly, a small creature uses smaller weapons and can carry less than a medium one. So you can have an 18 Str halfling and an 18 Str minotaur meet -- and the minotaur will be able to carry much more and do more damage.
Since I've seen things saying WotC wants to do away with video game style ability score bloat, this I think could help. You still get most of the effects, but not the ridiculously high scores.
My suggestion for 5e is: don't do this. Size should have an effect, but not directly on the stats. Especially if skills default directly off of ability scores. If a monster is going to make a Con save against your attack (or whatever the exact mechanic), it's really going to suck if they have a 30 score and you're a fighter with a 16 strength.
But size should affect things like your damage and your hit points, right? Right! But just do it directly. If you're large, you use bigger weapons and get, say, a +2 damage bonus. You get bonus hp per HD, or maybe even just a flat +10 HP bonus. You can still have a large creature with a 3 Str or an 18 Str -- but they can do feats of strength that a smaller creature can't. Similarly, a small creature uses smaller weapons and can carry less than a medium one. So you can have an 18 Str halfling and an 18 Str minotaur meet -- and the minotaur will be able to carry much more and do more damage.
Since I've seen things saying WotC wants to do away with video game style ability score bloat, this I think could help. You still get most of the effects, but not the ridiculously high scores.