I understand the sentiment, but not exactly the purpose. Are you suggesting we indict everyone who committed a crime in the past or limit it only to those that committed violent hate crimes against African Americans?
Furthermore, you raise a great point, that under our system of law, dead people have a hard time defending themselves an important feature of our justice system. Then each dead person you want to indict will require a public attorney at the least, meaning present criminals will have to be released because we can't provide them attorneys in the time needed to meet the "speedy" trial requirement under our law.
On the other hand, if you want to write a book and publish the names of every person you can confirm that participated in lynchings, you could do that, but again not sure of what purpose that would serve.
What I do think would be valuable given all the effort you have invested in understanding what happened is to capture that for posterity and then to expand its relevance to show how vulnerable marginalized groups in our society can be to violence. That would be a powerful gift to future generations..