"This is analogous to what creditors angle for in bankruptcy reorganizations" you are a joke. these companies are making money hand and fist. they aren't in bankruptcy. get a real job.
"The only feasible avenue for release includes a full conversion of the SPS. A write down doesn't help with the capital requirements, a conversion does."
I think you're wrong here. The capital levels (including CET1) increase by $191 billion when the SPS disappear from the balance sheet. It doesn't matter whether the SPS disappear by write-down or by conversion to commons.