Was thinking maybe downscaling then upscaling with nearest neighbour. Might turn out ok ?
Discussion
no idea but maybe this helps:
https://colececil.io/blog/2017/scaling-pixel-art-without-destroying-it/
I find midjourney produces artefacts/weird juju that needs a paint over tidy up in an editing program, if you're going for pixel art aseperite is a nice tool