I really like the #4 and #6 mainly because we are working on both. :) I totally believe that education industry needs a makeover because it is extremely fragmented and highly inefficient with very less innovation.
and the strange thing with this is that everyone agrees education industry needs major innovation but not much VC funding is being poured into it in spite of huge (billions) opportunity.
the textbook/education industry is probably the largest on the "change the world" scale. It would take a really adventurous and patient VC and/or Angel group. You would also have to have a good group of advisors and/or team members that knew the space. It's a long long term company, but at the end of the day it would probably have the largest impact. If I were a VC, I would fund the right team to do this without hesitation.
That's because there are powerful interests that aren't interested in innovating here: they like the industry just the way it is.