A slider to determine initial load-out would be nice, and have it pull from all sponsoring planets proportional to each planet's pop : sum of all those planet's population.

Although you would be able to abuse this by setting really far away sponsors, so the colony ship doesn't have to travel.

zero - you are right you could abuse far away travel by pulling troops from great distances. I think having supplies coming from cross galaxcy is a bit dumb. I'd prefer only pop and resources to be from immediate planets.

Ballin -  I think it would be cool if you could have a "migration" route. It would help immensely with population pressure and filling up new worlds. Especially since now planets output is based off population size. i would love to see that go live

i thought they mentioned some sort of population trade in a recent dev stream if so this should be included in it another option although annoying would be to build the colony ship empty and then you must send it to a world to pick up population.

From my design notes for Beta 2.

For beta 2, we will be adjusting the The Transport / Colony loading screen, as well as some of it’s behaviors.

1. All Transports or Colony Ships will now prompt when they launch, from a Shipyard, or planet.

1. Transports or colony ships launched from Shipyards, will take population evenly from all of its sponsor worlds, that are within 6 tiles.

1. Any sponsor world within range will be listed in the load ship popup, with a checkbox, (Default to checked). If the player unchecks a planet it is not included in the loading.

2. Transports or Colony Ships that are launched from planets, can only load from the planet they are launching from.

3. Shipyards that are beyond 6 tiles from any sponsor world, should have Transports and Colony Ships Disabled.

1. On these shipyards, the transport or colony ship should be visible but greyed out, and when selected, or moused over it should say. “Shipyard too far from sponsor worlds.”

4. Transports and Colony Ships that are STATIONED at Shipyards, or Starbases, will not eject their population and will hold whatever they have.

1. When a ship is ejected from a Shipyard, the ship should re-prompt as if it was just built, but the window should reflect its existing population.

1. If the player chooses to take more people, or leave people behind this should work in just like loading, or loading in reverse.

2. When ejecting from a starbase no population changes are allowed.

You can do that already, but you have to send the ship to the world. 

Where do you see design notes for Beta 2?

I think it makes more sense to still be able to build transports and colony ships, just not be able to load them.

By "makes more sense" I meant in terms of game-play, not realism. For instance, what happens if you start to build a transport then move your shipyard away from its sponsors? Maybe you want to build an empty colony ship and stop on the way to pick up your colonists, I think you should have that option.

lol I got a feeling doing that would break the game and ctd it.

A few questions regarding this:

1. How do you define 'evenly'? If I have a transport that requires 6 billion population, and I have 3 planets in range, will each world lose 2 billion people, or will the distribution be weighted by available population?
2. In regards to question 2, if the 'even' division of population extraction is just (required population)/(number of sponsors in range), what happens when one or more sponsors within range is insufficiently populous to provide its share of the population?
3. Why the 6-tile limit? Why should a shipyard beyond the 6-tile limit not be able to build transports and colony ships? There's no logical reason why I can't at least build the ship, even if I can't fill it with people.
4. The six-tile limit feels somewhat arbitrary, even if it's meant to represent the limit of how far you can move people in one turn. Perhaps it ought to increase with speed bonuses and be set at whatever your faction's ship speed without any added engine components would be? Or allow you to load troops beyond the limit, but at the cost of, say, 10% of the maximum troop load for each tile beyond the no-penalty limit?

I'll also say that I find the distinction between shipyards and starbases to be a bit odd, as far as the ability to change the carried troops or colonists goes. It seems to me that if I'm able to manage the transportation of X billion people to or from a shipyard within 6 tiles of the nearest colony, I probably ought to be able to do the same for a space station within the same distance.

6 tile limit is to avoid exploits. If you don't have a limit then you can set a planet across the galaxy as a sponsor just to contribute soldiers or colonists. 6 tiles has already been established as the range your shipyard can be from a sponsor without suffering penalties. 

If I can manage to ship materials 200 tiles, I can find a way to ship people the same distance. Beyond that, it's an arbitrary limit that bears little apparent relation to the game - surely the speed at which my ships can travel should have some impact on how far away a shipyard can be before it either suffers production penalties or ceases to be able to supply troops to newly-built transports. Further, this still doesn't justify the "seven tiles away and you can no longer build transports of any kind at all, whether they're filled or not" ruling.

Also, as far as the question of avoiding exploits goes, in that case it would be better to just give the shipyards a fixed area from which they can draw resources rather than the current sponsor system. I can't say that I see forward construction of warships to have significantly less exploit potential than forward construction of transports does.

I also did not suggest that the shipyard should be able to build the transport or colony ship entirely without penalty at extreme range. To be perfectly honest, I'd rather that the transports and colony ships did not automatically fill up with people from the sponsor worlds at all, as it's a bit too much like magical teleportation for my tastes. Regardless, if shipyards are going to be able to launch loaded transports and colony ships, I would rather that the penalty mechanic behind that be reasonably consistent with the penalty mechanic for production, rather than being a magic insurmountable wall six tiles from the sponsor world.