A quick and dirty workaround would be to increase the Strength stat on your character to extreme values.
Not the same as the mutation and one punch will pulp about any being (if that’s a concern), but it works and doesn’t require modding…
Not sure if it’s still useful for you or not, but I just added weight/volume reduction to the debug backpack itself. No need for the very strong back mutation.
I made a little mod for myself to adjust the backpack separately, so you don’t have to go back in and change it every time you update the game. If you want, I can send the whole thing to you. It’s got some other changes to character generation that require the bionics and CRIT mods (mostly just adding professions to the two lab starts). Give me a shout if you want me to pass it over. I can also remove my other changes easily enough if you just want the backpack update.