This blog shows what happens to these SSDs:
https://www.neowin.net/news/no-firmware-may-ever-fix-sandisk-extreme-pro-fails-and-deaths-as-it-can-be-hardware-issue/If you are willing to try something that is a little zany, cut two squares out of a thick rubber pad, then sandwich the PMIC and its support components between these rubber squares and gently clamp them in a vice.
I have actually seen a video where someone was able to recover an SSD in this way. Even more hilarious, and perhaps a little sad, is an official "repair" by that multi-trillion-dollar company, Apple, which uses exactly this technique to address a soldering defect on one of its motherboards.
As for replacing the PMIC with external supplies, this should work, but some care needs to be exercised. That's because the PMIC is designed to power up the supplies in a preprogrammed sequence. I don't know how strict this requirement is, though.