Tested ufoai-2.3-dev-28692 & the bug regarding the stairs is gone
A map-maker's conceit, perhaps, but I'm all for the removal of first-person view! It's enough work designing for the top-down view, and lets me spend time on the details that will matter from that view.
When I'm playing UFO:AI, the first thing for me to do is change the perspective with 'del' when the battlefield is opened, this looks & feels much better for me than the view from top-down...
Maps are optimized for top-down view, so many bottom and even vertical planes is not seen in isometric was marked as nodraw and is not drown at all. So first-view will be just ugly.
I understand that, but I am still imagining pressing 'v' & the camera flying into the head of my soldier who sees the alien standing in front of him - eye-to-eye
For me the big benefit of 3d graphics are moving, zooming, turning cameras & many different viewpoints...
But I understand the problems from a designer's perspective also...