Install to flash
I think that some operating systems allow you to install programs directly to the flash drive, if so, that would solve your problem. As for the image files of NT ms, a larger flash drive may support this install as well. I have at present a 32 GB flash Drive that would be adequate for that kind of installation.
If I have told you earthly things, and ye believe not, how shall ye believe, if I tell you of heavenly things ? John 3:12 KJV
εκεινον δει αυξανειν εμε δε ελαττουσθαι John 3:30