I bought the book D&D 5e Eberron Rising From The Last War. I have seen magical objects in it and I see the prostheses. That reminded me of a prestige class where the point was (more or less) to become a slab in D&D 3.5.
And then I saw that the bracelets (and similar magical items) are just forged, and my idea simply got crushed.
Since prosthetic limbs only give you a missing limb for a cheaper regeneration spell and cost you to be in tune with it (which is, for me, a great cost), why not improve it a bit by saying that it allows you to tune in to a bracelet (and similar magical items) even if you're not a war forge?
Are you unbalanced? If so, what point did I miss?
Annex: Since it has been formulated in comments (by @NautArch), I will say my ghess about my own question (and since I think it is not appropriate to answer it, I put it here).
My guess is that it is not so unbalanced (or unbalanced in the "still weak" form).
Having the prosthetic limb that allows you to use a bracelet (or similar magical items) costs 2 tunings instead of one (for me it is a lot), and makes the "can ignore the war forged requirement" somewhat weak ( but less weak than "you just replace your arm").
It makes the prosthetic member interested, similar to the prestige class 3.5 that has this characteristic at level 1 (level 4 of the PC) with other characteristics and for the only cost of its level, and fulfilling the requirement, that It's no big deal if it's your character concept anyway.
Even if 5e and 3.5 are different, they share many similarities that help determine if something is balanced or not.