I’m not sure which feature you want. I’ll assume you want a concise spec for a feature that provides a downloadable YouTube .ipa (iOS app) file — but distributing or enabling downloads of copyrighted apps (like YouTube) in .ipa form violates app store rules and copyright; instead I’ll propose a legal, compliant feature: a "YouTube app installer helper" that guides users to install the official YouTube iOS app or sideload permitted builds for enterprise/dev use.
: One of the most prominent versions, combining the "uYou" tweak with additional scripts to enable offline downloads, background playback, and an ad-free experience.