Hello Fred:
Here are some thoughts on your i915 situation. Testing was done with the Daedalus Starter Kit.
I have a converted Chromebook with an AMD chipset, so it is not directly comparable to your machine. But it also has great trouble with any operation that involves restarting X, like changing screen mode via lxrandr. It locks up with a black screen of death that requires a hard reboot. Luckily, I saw your trick of making a small xorg.conf with the desired resolution, so I can now switch it successfully from 1920x1080 to 1280x720 at bootup. The Touchpad app has a new Mode tool that handles this.
I have another converted Chromebook with a Celeron N4000 chipset and Intel i915 UHD Graphics 600 video. It is closer to your machine but with a smaller 1366x768 screen. It is quite happy to change resolutions in lxrandr, even if the aspect ratio is different. Restarting X works every time.
I don't know why your machine behaves differently, but I no longer think that this situation is the crisis that it originally appeared to be. There are enough work-arounds that it doesn't require major changes.