This mod will let you put a skin on a secondary saw. It DOESN'T give skins, it just give you the weapon skin tab to apply a skin you MUST own. While the mod is active, the primary saw skins are disabled.

Now let's wait for overkill to make a real bug fix, but in the meanwhile...

• Install the mod
• Set the skins on your secondary saws
• Exit to the main menu (to trigger a save)
• Disable the mod
• Restart the game

The skins should stay on the secondary saws even after disabling it.