A couple of people tried, but efforts and been unsuccessful due to how it is implemented in the game.
If it brings some hope, back in the original 2019 launch, sending to cold storage used to strip the paint job to default (and there wasn't paint scheme saving without a mod). And cold storage was limited to 50.
All of that got fixed by patches, so the upgrade stripping might get a fix too... eventually.

Originally posted by ุReshy:

Anyone able to setup a mod that retains the upgrades of a mech in cold storage, or able to add additional active hanger slots so it's less of an issue?

That was one bizarre, dare I say lazy fault in the game.

Originally posted by Pharos:

A couple of people tried, but efforts and been unsuccessful due to how it is implemented in the game.
If it brings some hope, back in the original 2019 launch, sending to cold storage used to strip the paint job to default (and there wasn't paint scheme saving without a mod). And cold storage was limited to 50.
All of that got fixed by patches, so the upgrade stripping might get a fix too... eventually.

Bless those EGS beta testers. Must have been a tough year and a half lol.