View editor and preview at same time

I would like to be able to have the editor and the preview side by side (two columns) so that the live view can be compared to the code.

I thought I would be able to theme this, but unfortunately there are some javascript bits to make it messy. Could a few changes be made to make this possible? Perhaps as an option in settings to either show or hide editor during preview?

The knock on effects are that the preview should always be visible (so not hide when button is pressed again), and the button would then be 'update preview'.

I think this would be far more usable than the either/or option where novices may struggle to relate code to the preview.

Will hack the JS for my own use, but can share if this is of interest.