Although I agree that it could be somewhat easier, I don't think it's possible to perform all necessary steps to create a working boot entry from within Windows, possibly any running OS.
I do think maybe it would be possible to improve the UX somewhat, what about having some app called "os changer" or some accessible user-friendly name, that shows a list of options with screenshots, short descriptions and perhaps some categorization/tagging/rating system (this one is good for gaming, this one has lots of support for old hardware, this one is user-friendly). Then if you select an option it starts to download the iso silently while it asks you to insert a usb-key, when you insert that key, it shows the contents if it's not empty along with a confirmation that it gets emptied. Hopefully after formatting the image has finished downloading, and it creates a bootable usb key from it. Possibly it could read system information to suggest a key to hold during boot, then reboot the system.
However you do it, I don't think there's any way around needing some intermediate to boot into. Come to think of it, maybe a live-distro where that intermediate basically is the eventual system seems very user friendly.
I do think maybe it would be possible to improve the UX somewhat, what about having some app called "os changer" or some accessible user-friendly name, that shows a list of options with screenshots, short descriptions and perhaps some categorization/tagging/rating system (this one is good for gaming, this one has lots of support for old hardware, this one is user-friendly). Then if you select an option it starts to download the iso silently while it asks you to insert a usb-key, when you insert that key, it shows the contents if it's not empty along with a confirmation that it gets emptied. Hopefully after formatting the image has finished downloading, and it creates a bootable usb key from it. Possibly it could read system information to suggest a key to hold during boot, then reboot the system.
However you do it, I don't think there's any way around needing some intermediate to boot into. Come to think of it, maybe a live-distro where that intermediate basically is the eventual system seems very user friendly.