Not quite the same, but we had a static member who had a stroke, and pretty much everything happening around her registered in her brain with a delay after that. Physical "high ping", if I can describe it as such. She raided with us quite successfuly, even if it took longer for her to adjust to some things.

Since you excel with pattern recognition, maybe you could tie positioning into that by creating patterns in your mind, such as "when A happens, I'm supposed to stand in position B". FF14 fights aren't always intuitive, but majority of them are pattern-based, so if you know what strategy you're using and what your role position is, you typically create the mapping of how you're going to move throughout the fight. Other than that, having a group of players who're accomodating to your pacing and having a lot of patience for repeating the same thing for hours (which, honestly, happens to most raiders, I think) would to the trick.