Cross-posting in reply to your question, though it's plausible ideas as well.
On a related note I have wondered if the Freedomites had any genocidal or even just eugenic polices about the handicapped or disabled like the Nazis did ? We know they would for black people but what about whites and others?
In regards to mentally handicapped people, they could be the among the first to be exterminated by forced euthanasia like they were IOTL by the Nazis. This will expand to people with incurable diseases, physical disabilities, and anyone deemed "life unworthy of life." With the Featherston regime deciding to use gas against blacks, it's likely the disabled would be used as test subjects in a TL-191 version of Aktion T4. Add that with the use of eugenics and scientific racism and it's more than likely they'll be targeted for extermination as well. This will also be applied to any of the CSA occupied territories in the US. Anyone responsible will be tried in a TL-191 equivalent of the Doctors' and Ministries Trials.
That could well be the case. I know that plenty of political dissidents were targeted first just like the Nazis did IOTL. The same could also apply to any labor unions in the CSA and they'd likely be targeted next. Soundwave's post postulates that there'd be plenty of whites in concentration camps separate for them, as is the case with Willy Knight prior to his execution. They'd likely also be used for slave labor and be subjected to an "extermination through labor" program like what the Nazis did. It's also going to be the case with the African-Confederates as there's a scene mentioned where Camp Determination prisoners were forced to build and expand the facilities ultimately used to exterminate them. Prisoners all around would be transported to wherever backbreaking work was needed throughout the CSA and occupied territories, in my opinion. This would likely be the case as well with blacks from the Caribbean along with their white and mixed-race counterparts.
point in fact, having just re-read "In at the Death" the CSA DOES in fact use white slave laborers in their Rocket Factories in Huntsville Alabama. Cinncinatus Driver and his truck convoy are used to transport them to a hospital, and the sight of these white prisoners makes him pause to reflect on the true depths of Featherston's evil. If I was reading it right, He knew the CSA hated blacks, but it never occurred to him that such things could happen to White people too.