When I was in Texas, a phrase that I sometimes heard was “might have could.”
Not sure of that one, nor the ilk of those from which you heard it. Maybe you were still over in Oklahoma? It’s a big country (Texas) and though we mostly speak english (of some sort), of that expression I’m not familiar. On the other hand you might take note of a far more common saying, “Don’t be ugly!” A former associate of mine (from Ohio) was so vexed by this statement she would say, “You’re born ugly! You can’t be ugly!.”
Denial ain’t just a river in Egypt. - Mark Twain
I heard that phrase from a woman in San Antonio, which is definitely Texas. I’ve since heard it from other Southerners.
What is funny is that the friend who always said it had one of the thickest Texas accents one could imagine. And I have a... well, probably mix between CA and MD accent. So one day we were talking, and I said the word “leg”, and she noticed that I pronounce it “layg” (long a sound) instead of “lehg” (short e sound). She said that until she heard the way I pronounce “leg”, she had never noticed my accent! That surprised me, since we have very different accents.