One of the major flaws of FO3 that really bugged me is the hard cap on stats and skills.
If your STR is 10 and you get into a power armor, your STR will still be 10. This means it's stupid to start the game with your STR at 10, because that's a waste of stat points (not just because your INT would be low ). The hard limit on skills was also bad, if say my small gun reached 100 I will have to dump points into other skills, even if I only want to be a sniper that shoots everyone. In FO and FO2, combat skills above 100 would increase crit rate and gun skills above 100 would let your shot remain accurate at even longer distance. I really hope I won't see the same limitation in FO4 again, as I don't see any good reasons to prevent players from creating extremely specialized characters.