RIght now, if a planet with 50 military production is building a ship that requires 20 more points to complete, the difference of 30 points is wasted and the player is charged for it. This applies for social production as well. Research is different, as the excess production towards a technology carries over to the next technology (unless the researched technology was the last in the branch, in which case the excess research is wasted and the player is charged for it).

I'm proposing to change the handling of excess production so that it's carried over to the next ship, building, or tech. The motivation for this change is to reduce the need for micromanagement by eliminating the incentive for micromanagement.

With the current system, there are sudden changes in payoff for small changes in input. Consider this:

Three planets building a 160 cost fighter in current system:
Planet A, 158 military production, 2 turns to complete (316 charged per fighter)
Planet B, 164 military production, 1 turn to complete (164 charged per fighter)
Planet C, 640 military production, 1 turn to complete (640 charged per fighter)

Three planets building a 160 cost fighter in proposed system:
Planet A, 158 military production, on average 1.013 turns to complete (160 charged per fighter)
Planet B, 164 military production, on average 0.976 turns to complete (160 charged per fighter)
Planet C, 640 military production, on average 0.25 turns to complete (160 charged per fighter, 4.0 fighters per turn)

And now for the details.

Proposed handling of excess social production:
Extra production is applied to to progress of the next building in the queue; the process is repeated if this extra production completes the next building as well. If social production remains and the build queue is empty, the extra social production becomes military production.

Proposed handling of excess military production:
Extra production is applied to building an additional ship of the same model; as above, the process of moving excess production is repeated, allowing multiple ships to be built on a planet in one turn.

Proposed handling of excess military production:
Instead of being applied automatically to the "next tech in the branch" as it is now (which is ok but not ideal), excess research should be stored and applied to whichever technology the player selects as the next research target. At this point (after user input), the process is repeated. So if you had a total research in a turn of 1200 and decided to start researching the Armor Path, at the beginning of your turn you see the following series of menus:
You've researched Armor Theory! (at this point, 1120 RP remaining)
Research selection screen: user selects "Titanium Armor"
You've researched Titanium Armor! (1040 RP remaining)
Research selection screen: user selects "Titanium Armor II"
You've researched Titanium Armor II! (850 RP remaining)
And now maybe that's enough armor, and I want to switch to Expert Minitiaturization
Research selection screen: user selects "Expert Miniaturization', progress 850/5000)
In other words, allow the player to select each technology when researching multiple techs in a turn.

These changes would eliminate the waste that micromanging seeks to minimize, and in so doing would obviate micromanagement of production. Moving to the new system would take a moderate amount of work: implementing the new formulae, modifying the UI for when techs are researched, rebalancing in light of higher (waste-free) production levels, maybe some slight AI changes. It would make a huge difference when it comes to the user experience, though, especially on higher levels where micromanagement becomes a big (and unwelcome) part of the game.