To be honist I don’t think that idea wi work well if ar all.
Several things to consider.
The data speed of USB slows down the more USB devices are plugged in so if somebody has a lot of devices conected there computer may not be able to sustain high enuff data rates via USB to play the video smoothly.
The previus potential issue will be even worse if the computer only has USB 1.0
There are numerus DVD player applications on windows and who knows if all of them will play DVD files from a drive instead of a DVD.
A flash drive will NOT be recognized as a DVD so even if the computer is set to autoplay DVDs it will not autoplay.
Again with all the different DVD player software out there I don’t think you could get a script to talk with all of them.
In addition DVDs all much cheeper then flash drives.
Sorry but I don’t think the idea is that fesable.
There are no “technical solutions” to your “artistic problems”.
Don’t let technology get in the way of your creativity!