I think terminology [1] is quite promising, although it doesn't yet do all of the above.
Previous thread: https://news.ycombinator.com/item?id=2559734
Related terminals: https://news.ycombinator.com/item?id=3227702 https://news.ycombinator.com/item?id=3910649
"What happened to TermKit?" on Reddit with a reply from the author: http://www.reddit.com/r/programming/comments/137kd9/18_month...
I'm thinking we'll need a terminal window that interfaces with bash but has overlays in HTML and other controls for scrollback, etc. Maybe a fork of an existing terminal.