I think that Professional Pilots won't be too keen on doing these things either. As Bus429 says, if engineering people have to get JAR66 licences to be able to sign for these things - at considerable personal expense and effort - why are pilots to be extended the privileges of the licence without the same rules being applied? Either the licence (and the fees that go with it) is necessary or it isn't. The practicality of the situation is that the work will be done by a mechanic, or an LAE that doesn't have the required company approval, at some outstation. The pilot will then certify the work. That certificate says that the work has been carried out using only approved materials and in accordance with the approved procedures, documents and manuals. I'd expect the person issuing the certificate to be competent in all these areas, including any relevant current airworthiness directives. As long as they are, it doesn't matter who signs the certificate, but an ATPL doesn't cover all these areas in the necessary depth. The tasks may seem superficially simple, but some have already used the Korry light example to point out one risk. How about wheel spacers for another? Some simple jobs aren't as simple as they seem.
Finally, I'll just point out that despite being a current LAE with type rated multi-category licences on several large airliners from two different airworthiness authorities, I am not qualified to certify any of these tasks on any aircraft. But the pilot would be? How distinctly odd!
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Through difficulties to the cinema