And you believe all of those things were not just possible but could have been sustained?
Yes, absolutely.
Do you think they could have accomplished all of that without turning the Reconstruction into a generational occupation of the South?
... what the fuck do you think Reconstruction was?
And you think it would have been economically viable
Yes, absolutely. Sharecropping is not actually great for the economy, and the South would remain economically marginal to the USA for decades afterwards.
and that the necessary long-term voter commitment would be there?
Yes. The only fucking reason Reconstruction ended in the first fucking place was a deal between the Democrats and Republicans over a disputed election.
"Hannibal Hamlin is VP when Lincoln is assassinated" is potentially all it would fucking take to extend Reconstruction another 5-10 years, and with greater results in the first 11 years too, for that matter.