Interesting thread.
My home brew 15' gate (made from chain link fence rails) has a solid caster wheel to help it roll into the closed position due to a sloped blacktop driveway.
I'm planning a rolling gate for my front yard entrance. Planning on a standard tube gate (for the structure) with fence boards added for privacy. Concept is to roll laterally behind the hedges. I'll need to level the area for the wheels to roll over, but it will either remain turf or get crushed rock or maybe pavers. I'm planning on manual movement, no power opener, so movement needs to be fairly easy. I'm not sure I want either solid or pneumatic tires,. but something in between might work well.