From your earlier videos I particularly like unusual or 'out of the box' type engineering tricks 'n' tips.
e.g. ethereal reverb, mock stereo acoustic guitar, that kind of thing.
For myself, I'd like to see some more guitar-related content.
As mastering is something that's very specific to the piece of music in question (and how it's been mixed), as well as requiring a particular listening environment and good, experienced ears, I'm not sure how much can be taught/learnt from a video.
Having said that I like all your videos so would buy another whatever the content :-)