Built this myself in 7 days. Took 54 hours. Not proud of how no life i went on building this, but its a cool build. You can find it at x:513 z:-4156. In the nether the closest portal is at x:58 z:-508 theres a cobble stone slab path to it. You'll need to max your render distance to see it from the viewing platform
vanilla cobble gens are capable of 120k cobble an hour (the one i built) anything faster when you need 90k is a little silly
I don't ever play vanilla, but doesn't a vanilla cobblegen involve standing there staring at it and actually mining?
you dupe tnt to blow it up, pistons push it into a blast zone, all automatic. Mojang wont patch tnt duping because of how relied upon it is in the redstone community until they replace it with something better in the future