Sorry, I've been away from the forums. To answer the last group of questions:
We are always working to improve performance where possible. I can't comment on any specific improvements in any particular update. In any case load times for the Foundry should not be longer than for star cluster exploration maps.
There will be limits set for objects of different types based on the impact they have on performance. These are pretty lenient, but they will give you some indication for which objects are more expensive than others.
That cutscene is automatic, but someday we may expose the ability to override it on a specific spawn point.
Yes, you can have bridge officers speak in addition to NPC's at any point in the mission.
You cannot currently choose the music. It is planned in the not-too-distant future.
You can control the overall lighting by choosing a "backdrop", which includes the sky or stars and weather effects. Eventually it will be customizable as a separate component.
Yes, you can customize the position and orientation of the player start spawn point.
We do currently have a very basic set of animations and behaviors that you can set on certain placed characters. We look forward to elaborating on the available behaviors in later releases.
I'm not an expert on our tailor, but I believe the costume pieces themselves are built to work with other costume pieces, and the geometry would break and look bad if you mixed and matched arbitrary combinations. I would expect the existing restrictions on costumes to remain in effect in the Foundry.
We do not have plans currently to allow terraforming or other customization of terrain. We have a decently large library of ground maps you can choose from whether hilly and tree-lined or barren desert. With all the combinations of terrain, building kits, and sky/weather backdrops, you actually get an impressive amount of variety to find your ideal ground environment.
This is not a currently supported feature, but it is on our wish list for the future.
I'm not sure those are currently in the library, but any object that we've used is relatively trivial to add. However, the ability to show/hide objects is not in the Foundry at this time, so I'm not sure they would be all that useful.