BAT actually includes Improved Graphics 2.0, and you can disable it by deleting or moving the file Assets/IG_v2.0.7.FPK. You can move it up one directory.
I have poor vision as well, and I prefer Blue Marble to both IG and the stock terrain graphics. It took a little getting used to at first, but if you like pretty graphics you might want to try it and see if you can tell the difference. It's actually much easier to see than IG, IMHO, though of course the stock graphics are easiest with their high-contrast colors.
