So.... Here's what I'm thinking:
All saves are made by rolling 15 or above on a D20.
When a save need to be rolled the DM presents these choices:
1.Acquire a new Save based on the current situation, write it down on your character sheet and get a bonus to your roll. The save is always written as save vs. ______. It is a save against a particular kind of hazard, attack, or situation.
2. Make a saving throw with no bonuses.
3. Use a Save that you already have on your character sheet if it applies.
The bonus, if you have a Save written down, works like this:
Each player can have a maximum of 5 types of Saves. They can't be swapped, removed or changed. Only one type of save may be gained per adventure. Existing Saves that PCs have acquired may be used in similar situations in the same way that the by-the-book saving throws in the original game could be (or kinda had to be) for example, if a character is being attacked by entangling vines he might make a save vs. paralysis because the vines are attempting to restrict his movement. Using this system, players could ask the DM if an existing Save that their character has could be used in other situations (that's what option 3 is above) For example, a character who is struck by a trap that releases a cloud of poison gas acquires "save vs. poison" and makes the save. Later, while staying at the castle of the Duke of Badlandia, and with the DM's approval the PC attempts to out drink the Duke and rolls to save vs. poison to do so.
Here's what I like about this: I'm into the style of play where a character's story is built in game, and having the name of the save tailored to the situations that the character has survived is a nifty way to embed that character's personal story into the mechanics of the game.
So one character might have:
Save vs. Pit Traps
Save vs. Mind Control
Save vs. Fire
and another character might have:
Save vs. Slime
Save vs. Invisibility
Save vs. Zombi Disease
This would be a good mechanic to use if you like building a character as you go and if your comfortable with the possibility of a little negotiation between the DM and Players.
This would be a bad mechanic to use if you prefer to have things clearly laid out in advance, and are less fond of making up character traits in game and justifying why they might or might not apply in a certain situation.