This seems like a pretty good shader for full on 2D low res games. I'd like to request its presence in reshade.
github.com/hrydgard/ppsspp/commit/7d8aed...e26e62ae14ec56745537

ReShade currently does not have proper upscaling/downscaling support. So it is not yet possible to port image scaling shaders. Although it is possible to downscale in ReShade it is really problematic at the moment. (e.g. Mouse position problems, works only in windowed mode, window size remains the same even though image is downscaled etc.)