I think you need a system for directly moving workers from x to y, while allowing multiple x or multiple y to be selected (so you can lets say select to take from "idlers" and move to all the others)

If you only drag a single bar, it takes from all the others (or puts to all the others)

I would make it so that you can select the "from bars" by clicking them, then dragging to each "to" bar from any of the selected "from" bars.

So if you want to move from "idlers" and "slackers" to "slaves" and "minions", you will click the first 2, then drag from either idlers or slackers to both minions and slaves.

There would be a "master" slider which you can then use to evenly move workers between the above groups. You should also be able to still use the individual sliders without deselecting your "from" and "to" selections. eg. if you were to drag ONLY idlers, it would go to both slaves and minions while slackers would stay unchanged.

I didn't play much MOO2, and really can't remember how that worked. Can you post a description?

It wouldn't work here.

MOO2, as per most large scale 4X games, does with a lot of abstraction. It replaces each 1M population with a single unit (a standing person) that you can drag between columns based on the function you want it to accomplish.

It works if you work with numbers between 1 and 20 but really gets out of hands over 30 or so.