So years ago I played a game were we fought on a wall. It was remarkably fun, and yes everyone involved was sober.
I don't recall the rules we used to the "T" but I decided to open a discussion about what they could have been or should have been.
1) Imagine that the field is actually a wall. This means any terrain would be "Ledges" .
2) Any time you move you are actually climbing, you have to roll if you are further then your height from the nearest ledge beneath you.
3) If you fall on a climb roll and fall back and hit a ledge, you take falling damage. If there are no ledges, you keep falling and die.
4) If you fall and hit someone, they have to make a falling roll minus the would be damage for the height the person fell from or they fall too.
4 alternative) If you fall and hit someone, roll for falling damage on both of them. Then whoever is living should make a climbing roll to see if they hold on.
5) Ignore the rule about not being able to perform any other action while climbing. You can climb into close combat but not fall into it.
6) Anytime you are shot at and absorb/take wound roll to see if you hold on.
Yes, if one person is climbing up and one is climbing down there is an inherent advantage to being the one climbing down. But for both sides, it is really fun. Havent played with UWZ rules/troops yet though.