Hi,
I understand that you would like to get to a Raw editing default method without variables like lens imperfections. However, this default will always be at least Sensor and In-camera Raw Compression dependent to begin with if you want to include the use of different algorithms in your test. You will never get to the perfect default editing method that works with any sensor and any in-camera compression. This is one of the reason for the existence of the different algorithms. Furthermore, what use is a default Camera-Editing method without including a lens? In real life there will always be at least one lens (not to mention a variety of them) in the game and a default editing method that did not include a lens is obviously not going to give you the best result once you include a lens.
Finally, if you “merely” want to test editing methods that work for any image, you will have to exclude the demosaicing step and just start your test from there on. I that case; why don’t you create a 16bit Tiff in a way that applies to your testing needs. Give it perfect lines, pure colors, build in contrast levels to your needs, etc. and convert it into a .dng. No real life photograph will ever match such perfection.
Hope this was helpful. Cheers!