Why not?

It sounds like looking for new gizmos without associated patents and then patenting them as yours would be an ideal strategy.

The alternative? Patent every gizmo yourself before release. Neat. A tax on innovation.

It's first INVENTOR to file. If you just see someone else's gizmo, you can't patent it because you are not an inventor.

All this changes is how it is handled when two or more inventors have overlapping inventions.

If by INVENTOR you mean APPLICANT... It is simply first to file. If you filed a patent for someone else's work, that work has to be successfully applied as prior art to invalidate the patent. If the existing work isn't sufficiently documented by acceptable publication, it is difficult to use as prior art years later when the patent is first litigated.

But, I am not a lawyer.

Don't patent trolls often operate by buying up patent portfolios?