Well Nick, 10'x12' is pretty limiting. But it is what it is. I like your Version 2 with the straights. Keep in mind you will definitely need access hatches. It's not a matter of if, it's a question of when. As well as derailments, you have to consider track cleaning and debris removal. Here's my recommendation. And hand-holes might be needed in the 2 corners at the right side of the room as well. A derailment in the tunnel at the back right could be a problem.
Good luck with your planning!