That would be great. Don’t know if it complicates matters but honestly if Cycles is used to render the previews when Eevee is the active renderer, that would be fine as Cycles doesn’t really slow Blender down noticably when previews get rendered.
Those useless previews are the worst. Eevee AND Cycles! We have thousands of options for everything in Blender, options for things no one needs to have an option for, and then we have those useless previews that stall the computer and waste hours of our lifes and no option to disable them. Please consider that people use Blender for production work with 8k, 16k, and in same rare cases even bigger resolution textures. Just try it out yourself please. Prepare yourself a nice 32k texture, drag it into Blender and see for yourself how much fun it is to work with that.
I don’t know I haven’t noticed a considerable slowdown with Cycles even with big textures. However in the image editor there is a slowdown for generating previews of high-res images.