Wanted to post this a few months before, but better late than never:
There are a number of tests with test equipment what you could already do with your existing equipment, and which would not require an extreme amount of resources.
Like with Oscilloscopes those done by Performa01.
But even with multimeters many basic stuff is almost never tested Like the crest mode with rare single signals (blind time).
The highest ohms test voltage, and with this, the in-circuit measurement capabilities(also for capacitance testing), the bandwith of the Volts or current range, or the DC-bias scenarios which we were debating about in the bm789 topic.
And of course, some test with some commercial household stuff would be also amazing especially regarding durability or repairability issues, but I agree the others here that it would not be easy to do.
Like light bulb light quality and durability test (although in the EU luckily there is some rule now that the R9 of the RA scale needs to be tested exquisitely, and also the flickering) but since the Fastvoice blog in Germany died down, there is less and less competition on the field of light quality it seems.
And recently I run into the mostly non existing thermal protection issue in hand blenders.
What is the maximum duty cycle and power an induction plate can endure, and what amount of enviromental electromagnetic radiation can we count with with different modells?
The duty cycle would be also interesting to test with radiation type plates.
And so on...