Stream has great sharing options like link and embed, it would be ideal if you could use only the sharing options for discovery.
Through the sharing options you can Link in Yammer, Team, Outlook, etc and Embed in a web page, SharePoint site, LMS, modules and have users encounter the video first there in a specifically created context.
I'm thinking an option to unlist/hide-from-search OR a some kind of SPOILER ALERT warning!
This is all separate from the secruity of the video. Just like spoilers, you can be spoiled if you want to be, but it would be better to give viewers and creators control.