Just by curiosity: why should I use a fog VM rather than a fresh install? About the switch: I guess it’s nog problem to plug the laptop directly in the campus switvch?

Our school has 3 campus places with each 2 computer rooms with 20 pc’s; we reinstall all pc’s twice a year.
Setting up 3 fog servers is financially not possible. We are thinking of dedicating a laptop with an external usb disk as a (mobile) fog server.
Would this be a realistic approach? Are there any specific caveats (e.g. each campus has a different subnet).
Thanks in advance
Chris