Good points indeed. Another argument would be that with a less stable heat sources such as open fire or propane range it might be hard to maintain the proper temperature manually, so the automatic pressure release should be able to amend that. Besides, in case I would really need to maintain an exact pressure value - I can still use the gauge to set and control it, while simply loading the jiggler with some additional weight and switching to the manual temperature regulation.

The source I used was some state canning club web page. I don't have that link at hand (it's on my home PC).

Also installing a jiggler will make story telling more family friendly, as I wouldn't have to use "petcock" anymore

By the way, the weight regulator also should have a limit to its life, as its surfaces should change with use. It would be nice to figure what could it be.

The image is indeed impressive, however the All American Canner should be blowing in a totally different way (the Mirro canner is pictured, which is jiggler based by the way; probably it was the gasket failure). I cannot imagine the lid separating from mine like that. Most likely it will simply spew out the petcock, or the gauge, or the safety valve first striping the threads. I doubt it is possible to tear trough such a thick cast aluminum wall (except you have a hidden crack already).

Regarding the emergency release valve, I have one installed. It looks clean. However, the petcock construction is basically the same emergency release valve with a spring holding the ball against the opening. And you are testing it's working every time you operating the canner. So, I think, the higher side is quite safe as it is now, as you will need an enormous heat to overpressurize with the petcock valve open.