wouldn't youtube-dl + mplayer be fine? if mplayer is compiled with openssl and/or gnutls it would be as easy as
if mplayer with openssl/gnutls is not available one can just use youtube-dl to download a video (yes, you can choose the quality to be something playable) and then play it with the player of choice
i still haven't tried because i'm really busy these days, but it should be really doable: in fact i do it everyday with my laptop (an overgrown IT basically ;D)
if someone is really brave he could compile mpv and use that... but dependencies are a pain...