(Throwing two title related questions together for avoidance of repetition.)
I wasn’t able to find GRRM lamenting that – indeed, I think he finds the simplicity of the titles one less thing he has to worry about, like the gender of horses and the width of hips.
But if we were going to start over from scratch, I think I would avoid copying historical systems too closely – baron, count, duke, earl, etc. all have specific cultural meanings that don’t necessarily work in Westerosi contexts.
Rather, I think I’d like to build on existing Westerosi terms and just use them more systematically – so no referring to Ned Stark as “Lord of Winterfell” or “Lord Stark” but rather “Lord Paramount” or “my lord paramount” being the correct form of address – so you’d have Lords Paramount, Lords Principal, Lords Ordinary, and then landed knights and masterly houses (which I would also clear up a bit – if the title of “master” is going to be a recognizably northern thing, there should probably be more than two examples in the series, and I feel like they could have sprinkled in some more masters among the ranks of Robb’s bannermen).
What is the correct use of the honorific “my lord”? We see it used as a general term to refer to anyone socially superior, used uncontroversially to refer to Tyrion and Jaime, but apparently controversial when applied to Edmure before Hoster’s death. What is the correct usage?
The controversy shouldn’t be over Edmure being called “my lord” – that is right and proper as befitting the heir and immiment next Lord Paramount of the Riverlands – but over him being referred to as “Lord Edmure” before the death of Hoster Tully in ASOS.
As you say, “my lord” is used to refer to social superiors as a matter of courtesy, but it’s not a title with legal rights and privileges in the same way that “Lord” is.