@Snowstorm - you present an admirable approach to this problem.
In response to a suggestion of repair I would query how they can demonstrate that this flaw is not a manifestation of a weakness in this piece of metal, that may be present elsewhere in this part as a structural if not a visible defect. Only a full x-ray analysis would be able to guarantee the flaw was localised to the visible defect, and in all probability that is never going to happen.
I am a little surprised that Tesla haven't simply pounced on this, grabbed the car back before the news gained too much traction and would argue that it is a mistake for Tesla not to have done so.
Of course it is your decision, but I certainly would not accept the car back.
In fact, that such an error could escape Tesla QC seriously concerns me, and will absolutely be a factor in my next purchase.
Tesla can no longer count themselves as a startup company, they have 5+ years experience in the MS, more than enough time to get this sort of thing right.