Well, for production and sharing thing, here's my two cents.
Money equates to the value of given goods. Production is a concept of what it takes to produce those goods. Now unless you mean transferring of partially finished goods to be completed somewhere else, that's not exactly viable. I mean, the energy wasted getting goods to space would be better off producing them on site of a planet. I mean, we're likely talking about Tens to hundreds of billions of people, and the consumption of goods on such a massive scale that it becomes impractical for a world of production to do anything but transport raw materials, finished goods, or food from one place to another. It's not like making Microchips in Thailand, Soldering them to motherboards in Taiwan, shipping them to the US to be put in a computer. We're talking about building chips in Thailand, blasting them off to the moon, finishing them on Titan. It's not worth it by any economic sense.
So if production was to be transferred from 1 planet to another, it'd be as a full product, not partial goods (IE, production points to finish certain things.) Perhaps being able to build simple colonisation modules. (Which I'm unsure if someone suggested earlier in the thread.) As something you could move onto a ships cargo bay. The colonisation module would be a simple all-in-one devise that's low-maintenance but high original cost, that is set up on site. it produces a bit of food and a bit of goods. This could jump start budding colonies, if you build larger colonisation ships, upon landing on a world, the ship get's converted to a number of modules based on the size of the colony ship. This way you eliminate "rushing" using money and the need for production sharing. Eventually the world will develop actual economic infrastructure and join the empire on a galactic scale and when this happens, those modules wouldn't produce enough goods to be worth their maintenance and perhaps a "Scrap all Colony Modules" button could recycle some of that material (or move them forward to additional colonisation efforts.)
As for sharing population. Would a world really be drained of people in the event of colonisation efforts to the point of endangering other parts of the empire? I mean, I'm still quite unsure of the scale we're talking about here, but if the empire's ships don't represent the civilian sector for ship production and trade, could a world even lose, say, a billion workers even to go to a new world to work and build new lives?
If planet A has 10,000,000,000 and Planet B has 1,000,000 people... truly what sort of global effort would have to be made, how many tens of thousands (or massive size ships) would be required to divert to drain enough people from planet A to planet B to endanger the planet. So except for player diversion of population, natural growth for planets should be based on an empire's modifiers, racial modifiers, and a flat planetary appeal (to account for the ability to colonize, and terraform) and some population should be drawn from nearby planets with higher population. Distance would also deter larger numbers of people from being drawn from halfway across the galaxy. it's not a month-long ship ride from London to New York, it's a galactic trip. Sure, some families will make the journey, some probably representing 1-5% of the population. A population that could soar up to 10-50 billion people. It becomes rather insignificant and tedious to even account at that level. Not to mention, especially if we're accounting for humans. If you're on a desert world you either like it there, you're forced to be there, the job pays reaaaallly well, you don't have the financial means to leave or... you would have left anyways... So you can't really judge that sort of appeal for why a specific planet would be chosen to draw population from. You could say that the other worlds are "filled up" and you couldn't really go there... but in terms of the billions, individuals don't really matter, and populations are likely moving from 1 planet to another constantly through "civilian means" (unless you are a tyrannical police state which controls population movements.) but even still, if you want trade, you're not stopping your freighters, and troops. Troops have families, and it's likely a big mess which doesn't truly need to add to the complexity of calculations going on in the game.
Colonisation Catch-all Module that you can load into freighters and any ship with cargo space, drop off on the world. bam, instant New-World Factory/Farming Equipment.
Pack them up or Recycle them when you're done with 'em.