I'm currently researching a gameplay demo I’m planning, however there are a number of physics challenges I believe I will need to overcome, I was hoping I could draw upon the experience of the Bullet community to evaluate whether Bullet can solve my requirements, I must admit now I am no Bullet guru and I have only dabbled.
This is my scenario....
The main zone is zero gravity.
The player will fly around this zone and is required to land on and walk around various objects.
These objects have there own centre of gravity, some may be spherical, and others may be flat platforms or even a cube for example.
This is how I would try to achieve the above, this is all up for debate of course

When it comes to the creation of the physics world, I create the main physics world with zero gravity.
When the player is within a certain range of an object, I apply a 'fake' gravity in the form of an impulse in the direction of the objects centre of mass
I give the object being landed on a low friction value so the player can slide around the object as if they where walking on its surface, whilst the fake gravity impulse is still pushing them down onto the surface?
To detach the player from the object, I would apply an impulse in the opposite direction to the 'fake gravity' to propel the player out of the objects range.
Please let me know your thoughts.
btw, this is not anything on a planetary scale, more of an experimental game play idea

Cheers,
John