Might even be able to put them on remote storage, how fun.
Unfortunately current layers are apparently all kept in memory and that scales accordingly to:
width * height * channels * [size of the channels](
https://docs.krita.org/en/general_concepts/colors/bit_depth.html) (so, for a 1000×1000 16-bit integer RGBA image: 1000 × 1000 × 4 × 2)`
Then multiplied the number of layers + 2.
All to say that my ~2GB spare machine lying around would be a bit tight.
How vexing.