Hand counting of paper ballots is a highly parallel process that can be done quickly at any scale. The only reason to introduce counting machines is so that someone can extract money from it.
Further, each precinct has to be tabulated separately. The poll site I ran for years had 5 precincts, roughly average. We'd have 400-800 ballots per election, depending.
One change that would make manual counting more feasible would be to split our ballots into federal, state, local.
Every election administrator I've ever met opposed manual counting. Mostly because it's a lot of work.
A group of intended to run experiments to determine the effort, cost, accuracy of manual counts. Simulate a real election, eg print up marked ballots where the totals are predetermined but not known to the counters. Alas, we never got our act together before every one burned out.
PS- Any tabulation method has to accommodate marking errors, aka adjudicating voter intent.