[Little Ray]

Dyson proposed breaking up Jupiter, Saturn, Neptune, and Uranus, just for starters. Each of these worlds is many thousands of times the mass of Earth. So there are your "several thousand planets." I think they'd have to do some large scale transmuting to do this, but that shouldn't be a problem for a fledgling class II civ.

Also, except in SF, the "sphere" is more a bunch of planetoids orbiting the sun in loose formation than it is a solid sphere. Talk about giving computers nightmares - imagine having to keep track of billions and billions of orbiting bolides...

If you want to get really ambitious, there is the Alderson disk... definitely for class III civilizations only.

Or if you're stingy, you can settle for a Ringworld. Assuming you can figure out how to make scrith...

[boris]

Yes, both the Ringworld and Dyson sphere have been shown to be unstable; ie., both require a negative-feedback active controller to keep the star centered. Eventually such devices will fail, which will rapidly reduce the property values on such artifacts.

--Boris