Possible to use resized image assets in resource folder without access to original assets?

I am trying to build a portfolio style site with large amounts of photos, structured into albums. I currently drop the photos into the asset folder and let Hugo do its resizing magic which works well.

The problem is the size of the assets folder (several gig and growing) I tried to move some older albums into an external repo (as submodules) but on every build, hugo insists on checking out all assets first. This is unnecessary, as my albums are virtually immutable and the resized images are available in the resources folder. Yet the build process requires the presence of the original images first.

Is there a way to trick hugo into resizing the images once, then using the resized image directly, without pulling the original image, on consecutive builds?

No, the name of the resized image is partly based on a hash of the original.