[Cyberthal]

There is no kinda idiotic. There is a somewhat stupid.

A Dyson sphere is foolish because one can simply build a small local fusion reactor instead of using the giant free one nearby?

Imagine a sphere of reflective particles around a star. Planets within would never experience nightfall. Free energy would be everywhere. Sounds useful.

Moreover, such a solar system would be difficult to detect. If it is mobile, and uses a low-signature form of propulsion such as UFOs exhibit, then it would be extremely elusive.

This solves the problem of someone launching stealth asteroids at one's base at relativistic speeds.

Moving a solar system presumably requires tremendous power. Using a star as the fusion reactor presumably helps.