as you mentioned, you really don't need clamber for this... just geometry and devices that allow you to scale the map.
H5 maps are taller due to clamber effectively increasing the heights players can reach, but maps don't "play" any more vertically than they ever have. arena maps are still, typically, just 2-3 levels and the effective ranges of all the weapons have been increased to negate he stretching that clamber and sprint required.
i just don't get the verticality argument. Prisoner and Construct are vertical maps, no clamber needed.
personally I'm not anti-clamber. but I'm against stretching maps so that players HAVE to clamber to reach jumps that would otherwise be crouch jumps. forcing players to put their gun away isn't good for Halo. period.
I've come to believe clamber is a pretty silly mechanic. Sprint at least presents you with a real choice (move fast OR be able to shoot gun), rather than clamber, which 99% of the time functions as just letting you jump/higher farther. Even when it is a choice (places where you could crouch jump), there is very little risk/reward with clamber since it's not much slower than a proper crouch jump. There's just not much of a penalty so it ends up being used constantly.
Personally, I would drop it, add a little visual flair to crouch jumping (thrusters effects or something) so scrubs will be impressed, and adjust the map geometry accordingly. Alternatively, they need to monkey with the risk/reward to make it actually interesting and not simply a stat boost of what you could do anyway (jump).