Subterranean Adventures is my D&D hack that I've been teasing for a hundred years. I just need to write the damn thing.
Anyway. "No saves? Blasphemy!" They've been in the game since forever. Yes. And they've also changed with each version. For some time, Saves were a static number you rolled under. There was also a fair number of them. Some reimagined versions of the game boiled it down to just one number. Then they became roll high and there were just three of them. Then they turned those three into "defenses" and re-introduced the static save (just one), except you now roll over it. This is basically just a roundabout way of saying that the constant changing of the mechanic gives me licence to change it further (Because what I'm going for is edition-agnostic. ie. it shouldn't be recognizably derived from a single edition, but familiar across all.).
Ok. One of the saves in classic D&D was Save vs Dragon Breath (or Breath Weapon). So when a dragon breathed on you, you rolled that. Except it was/is also common practice for classic D&D modules to repurpose the core mechanics in the context of the adventure. So it would be perfectly common to roll "vs Dragon Breath" when the dungeon ceiling collapses on your head. It becomes circumstantial. And it's not really Dragon Breath anymore, but something more like Save vs...Area Effects? And then that got folded under the Reflex Save after 3rd edition. So you'll notice that the saves are always rolled vs these broad categories of "catastrophic events" (as someone called them somewhere), it's just the modifier/target/subsystem/method of rolling that's shifting.
The other type of save is the one that ends ongoing effects. For example in 4E whether you're on fire, stunned or poisoned, you roll your save at the end of your turn to see if it ends (as a side note: this resolves the problem of tracking lots of "lasts X turns" effects). But there are also spell-specific or circumstance-specific "saves" that aren't really saves. For example in the Pathfinder spell Entangle, the entangled creature can make Strength checks to escape entanglement (ending the condition).
In Subterranean Adventures there are seven basic rolls, the core I'm starting from: six Ability Checks (I'm probably going to call them Tests) and the Combat roll. The number of Saves and the method of rolling thems is already very malleable, as evidenced by the history of the game. Classic D&D had five saves that were not particularly tied to anything else, in fact they were a completely separate subsystem that just vaguely interacted with the stats and class. But post-3E D&D has taught us that saves are (or can be) analogous to stats (Ref-Dex, For-Con, Wil-Wis in 3E and then Ref-Dex/Int, For-Str/Con, Wil - Wis/Cha for 4E). So what I thought was the obvious step was to rework the classic categories a bit, expand them into six and tie each one to one stat. Except there isn't really any reason to keep them as separate numbers at that point. Subterranean Adventure Saves are simply Stat Checks.
There is, I think, a great deal of streamlining, rationalization and my own aesthetic preferences baked into how the SA save categories are organised (or rather, which stat handles which "catastrophic events"). This goes against my mission statement of keeping everything "as is" in the original D&D texts, because I'm doing something new*, but:
1) there isn't really anything as-is in the original texts relating to saves, because it changes dramatically with each edition
2) since there aren't actually any save rolls as such in SA, I'm not really inventing new mechanics, merely saying "this is a stat roll" in relation to certain in game situations (You've walked into a room with an arrow trap? That's a Dex roll.)
So there you have it. The way specific situations are re-delegated to specific stats is perhaps a bit unorthodox (breaking down the various uses of the "Will Save" was interesting), but I'd like to believe it makes sense in context of the game. But more about that at some other time.
*My idea with SA was that I shouldn't invent any new mechanics for their own sake, but only use what could already be found in the published rules.