Though: an alternative approach did occur to me yesterday, and it's been becoming more attractive to me today. What if we simply split the Leg enchants into Leg and Feet enchants. Feet enchants would be anything jumping-related. Leg enchants would be everything else that's currently leg-related.
My train of thought is:
1. Screw attack never really hurt Metroid, and it was an infinite jump. And it was darn fun, actually.
2. Players being able to have increased mobility is darn fun here. Does it change the nature of the game when they get that? Sure. But it's a key thing that makes them feel more heroic and powerful, and taking that away (or never giving it to them in the first place) undercuts that.
3. Having increased jumping mobility also of course can mess with the balance of the combat somewhat... but then again the combat can be balanced for that. If it's expected that you have double or triple jump by the time you reach the second or third continent, it's not like that's a blocker. And in terms of the combat balance, you still have to dodge the enemy shots and land your own shots, no matter how many jumps you have.
4. Being able to dodge falling damage with this isn't terribly of much concern to me, and we could actually just change it so that jumping at the last second doesn't help with that or something. Though that might feel odd. At any rate, falling damage is one of those "whoops I slipped up" sort of things, not something that is a focal point of the game in the first place. The only reason it was added was to actually give a sense of height and risk, and you retain that just fine if you know you have to double-jump at the bottom of a pit to solve the falling bit -- in other words, the sense of danger remains, but that's also tied to your own sense of power and skill. Making things more fun.
5. Similarly, devaluing the wooden platforms is... really a good thing, I think. Sure, having to place wooden platforms or crates sometimes is interesting. And some of the missions will always require that. Certain areas in general will still need those either way, because of the way overhangs are or because you don't know what you're jumping down into, or whatever. So it's not like their utility goes to zero. But not having to constantly be placing wooden platforms is actually a GOOD thing. Just when players are getting sick of that, hopefully they are getting double-jump. And again, specific missions can always bar the extra jumps as needed (just as specific missions give you extra/infinite jumps).
6. So really, the only problem in my mind at the moment is that double/triple jump are so awesome that nothing else makes sense to use once you get them. So why not just move them to their own slot, and have done with it? Then the other leg enchants suddenly are attractive and interesting (maybe the regular jump height enchant stays there, too, to compete with the other stuff that gives you mana increases as well as powersliding or speed or whatever).
Ultimately it comes down to what is most fun. Is it fun to be limited in mobility? As Keith has pointed out to me in the past, that's actually one of the least-fun things that a game can do to players. Players almost always pick speed buffs over anything else. Why is storm dash so darn popular, right?
If balance is a concern, I still don't think it's a matter of balance between double/triple jump and the other leg enchants: that just makes for an un-fun choice by nature, I think. And thus the issue of dexterity really becomes moot -- we don't need dexterity, we need another slot. The question of balance is if the double/triple jump stuff makes the combat too easy (it doesn't affect the hardcore platforming sections at all, recall, since you have to wear a heatsuit which disables them in the first place -- that's the main purpose of the heatsuit, actually, and why it exists from a gameplay point of view).
So in that regard, if we're worried about this being abused in combat, why not do what we did with storm dash? Each jump you take beyond the first makes you take that much more damage until you land (except in umbra vortex missions or other infinite-jump situations). Heck, then we could actually introduce quadruple and quintuple jump enchants, and the risk with them would simply be that they would have absolutely immense incoming damage to you if anything touches you on a further-in jump. That would really be quite a stiff risk/reward if your 5th jump meant that anybody doing damage to you during the 5th jump did 500% more damage or something. Ouch. That would keep me more inclined to double-jump most of the time, and occasionally triple jump, right there.
Either way we avoid the need for an extra stat, and instead exchange that for a new enchant slot. Because, let's face it, a new stat that takes away abilities just isn't going to be well received. Even if people here on the forums agree now, it's only going to be a matter of days after this hits the non-forumite players before we start getting new players coming in and registering and raging at us. This is a game about being magically powerful, and I'd rather figure out ways to have the world react to your increased power (and it largely does) rather than kneecapping your power.
(Shields are a different matter, perhaps, but I'm still trying to figure that one out.)
