"If you put the code in mu-plugins, then it would simply check if NOT the On-Site, then turn off. Acts like a functions.php for all sites in the network :)"
Sorry, I'm not that technical, does that mean creating a plugin with just that one line of code in it? I understand what you're saying to do, but I don't know exactly how to implement it. I've activated site wide plugins, but I've never made a plugin. Would this be creating a plugin to activate, or create a functions.php file that goes in there.
Thanks for the reference Andrea, I've already have wpautop turned off via my functions.php on my root theme, affecting all blogs, but then a team who doesn't know html needed to have it on for just their site. So I need the easiest way to turn it on for just one subsite, b/c I don't want to jack up everyone else's blogs who know html and like it off.