This is a great thread and love seeing everyone's vision for modular walls. I made 10, 10'x10'x3' movable walls for our two exhibition spaces. I fabricated frames using 2"x2" steel tubing, and rolling them around on 5" casters followed by traditional framing using 2x4's skinned with 3/8 ply then drywall. The gap at the bottom is filled with bamboo flooring that matches the floor and base board so it looks pretty seamless. Here's a quick link that our Media Relations person put together.

https://www.youtube.com/watch?v=E3SrGzAsRBE