Guided lessons by style.
Right now guided lessons are all very generic. While I fully understand that for the beginner level stuff, it would be nice if after a certain point you could select a genre or similar, and the songs learned for those lessons could be picked from that genre.
It may also open up other areas to learn, for example eliminating skills you don't need to worry about for metal, or including skills you do need for (as an example) flamenco guitar.
F Reid commented
This would be great a Jazz course in particular teaching improvisation, and relevant modes as a start
It seems obvious, but they should have some Genre specific lessons, especially at the higher levels: Blues, Country, Rock, Metal, Pop...Jazz...it is surprising that they do not.