Robot Race (Screws) - Junker Ability

homebrew
question
#1

So I’m homebrewing another Race Type which are program free robots, basically they can do whatever they want with no constraints.
I have an Ability for them called Junker which allows the removal of a limb that can be replaced with any machine type but it only lasts for 2 D12 Hours (Chance for 24 hours) until it falls off.
The Mastery version of this is 2 Limbs can be replaced with a choice of one being permanent and the other being 2 D12 Hours.
Should this be replaced with the one limb is permanent rather than a choice of 2 or should I change the idea of Limb Decay for something else?
Maybe have basic Junker Ability be a Limb Removal (no limit) and have Master version be 2 Limbs?
Any Ideas

#2

What if mastery is an additional (third) limb, permanent but restricted to just that machine type?

#3

I think that would be cool so you could equip a single hand weapon or item. Now the regular ability is to be able to remove your own limb and replace it with a machine type but it’s only temp (2 D12).
Should that change or does it work? I’m on the fence because I don’t want players limbless but I figured they’d keep the original in a “compartment” or something