I partially agree. It's not feasible to expect the patent examiner to reduce a technology to practice, primarily because a lot of physical technology requires very expensive equipment and some skill to master (chemical vapor deposition chambers for thin films for instance). The ownus should be on the applicant. However, it is certainly feasible for an inventor to demonstrate a working prototype for each claim. Based on the number of rediculous awarded patents I've reviewed over the years, I imagine simply requiring demonstration will probably reduce the number of patent applications by 90%.

This requirment would have many benefits. However, a down side is that not all entities have the resources to build their inventions. If I come up with a new idea for an efficient rocket engine, I would have to license the idea to a SpaceX, etc, to get it built. But it would be difficult to approach a SpaceX and secure a license without first getting a patent.

You will need the resources to build it eventually. You can easily protect yourself from an individual entity stealing your ideas using a Non-Disclosure Agreement (NDA).

Not always, but in general, a proof of concept prototype (built in parts, at small scale, or simulated) will be an order of magnitude cheaper than a production unit.

Would a white paper for a free energy generator be accepted to a respected peer reviewed journal? Probably not, but there are tons of these truely worthless granted patents out there diluting the system. I strongly believe we need inventors to prove their claims via demonstration, one way or another.