First, unlike P. obsoletus, there are no recognized subspecies of P. bairdi. We recognize that individuals found in Mexico have a lighter color compared to those found in Texas, but they are still the same species. I would compare this to Eastern Garter Snakes. In some areas, they are dark blue in color with white forming a striped and checkered pattern; while in other areas, they are a light brown with a cream color giving them their pattern. They don’t look the same, but they are not placed in separate subspecies.
If you were to cross a Mexican with a Texas Baird, I doubt you would get anything that you couldn’t already see in certain locality Bairds. The one difference that you would find is that the color pattern that you would see on the locality morphs would be stable; while the crosses of offspring from your snakes would give you snakes at both ends of the spectrum and a lot in between. Since at hatching, they both look the same; a person buying such an offspring would have no idea what they were getting.
Do we really need more “science project” snakes? What is wrong with the color patterns that nature has produced?