Today, I've been thinking, computing to see if there's a solution that uses beamsplitter cubes, prisms and total internal reflection to pipe the image instead of a large combiner. I got this idea from seeing the range of Epson AR glasses.

It certainly looks geekeir though. There's also the issue of being able to hold all the parts together. A lens of some description will have to exist right after the beamsplitter cube to redirect the Field Of View light paths so that they don't hit the walls of the glass. In the below image, the white is the FOV cone and the green lines are lenses. The blue line is the beamsplitter reflection. It's possible that I could make the beams parallel up until the lens closest to the beamsplitter, meaning that the one closest to the white arrow could be omitted.