To be honest I would rather be able to directly control the funds allocated to Military, Social and Research, with a total funding limit determined by income, and individual funding limits determined by just how many factories and labs you have available.
What this means is that you won't have to build an insane number of labs and then run them at 30% efficiency to keep up with research, if the other 70% is going towards ships and buildings.
When you are funding Military or Social less than the maximum, then Focus will ensure that a planet gets maximum funding in that area, but obviously this decreases the funding available for planets that don't have Focus in that area.
When you are funding Research less than the maximum, funding will be distributed automatically to your most effective (cheapest) labs first. Obviously, this means you could have some labs on standby still costing maintenance, but it's useful to have the capacity there when funding is more readily available.
Having a total funding limit makes it more difficult for a human or AI player to run their economy into the ground. That's effectively what the sliders do, limit your total spending. All I'm suggesting is that you should be able to limit total spending and still have the ability to prioritise projects without having to drag sliders around for ten minutes trying to find the happy place between progress and 'on hold'.