I disagree. New money won't care whether the seniors are cancelled or converted to common prior to the re-IPO because neither of those, vis a vis the other, would affect to how much capital has to be raised or how many shares the new investors get.
Petrobras raised $70B, so I don't see $100B as all that absurd. The large necessary capital raise size is due to the 2.5% minimum capital requirement in HERA, at least if it happens in the next couple of years.
Enough core capital for what? Release from conservatorship? That's decades away with only retaining earnings, even with the recently-lowered capital standards.
There isn't any reason to relist the shares prior to the re-IPO anyway. And that re-IPO will be necessary for release from conservatorship prior to the decades-long timeframe.