Oh, I did that before posting to this list.
By the way, my iPad’s storage was probably full. I was listening to a podcast after a couple of weeks after not doing so, so the Podcasts app continued to download pending episodes. I had about two gigs available earlier.
That’s probably why my iPad crashed while playing a podcast. At the time I attributed that crash to the many random crashes people have reported on iOS 7.x, so I hastily started the OS update to end the crashes. Bad idea.
It seems that the reason the update failed is that the download couldn’t finish because there was no space available on my iPad. The process that actually installs the downloaded package attemped to install a package that was not downloaded in its entirety; bad updater, for installing a bad package. But even badder software-update starter starting the update process with so little space available on the iPad.
If my hypothesis is correct, my iPad should’ve checked the available space before attempting the upgrade. There should be a free-space requirement of at least a few gigs before starting the upgrade. There must be no upgrade attempted when the minimum free space requirements are not met. Keeping the user’s data safe should be the first priority of the update process.
I just added another feedback item describing this hypothesis.