Maybe it's just me but but I'd like overflow to be addressed in the game. Like for example, needing to research something to get to that point where you can complete more than one thing per turn. To players, it is 'lost' production because it doesn't carry over, but in the actual setting of GalCiv, it's production capability that could be theoretically utilised if the overseeers in the slave pits (for example) know what's coming next and can get the workforce to the next job really quickly.
So for example, you could have a technology (probably very early on) which allows full overflow on a planet when the next improvement is being built in an adjacent tile. You could have a technology for full overflow when the next ship being built at a shipyard is the same hull size as the one just completed.
It does mean that to start off with, overflow will be lost in ways that are understandable, and later on you won't lose any. So if you don't like micro-ing sliders, well, you won't have to.