Aspect of BOZ said:
i have another idea... all of the above?

there are 333 gems of course... and we're not going to give attributes to each one or anything. we could say that each gem has its own power, useable 1/day, and list some examples of common effects, such as: functions like a metamagic rod, functions like a potion, summons a creature, absorb spell energy, work like ioun stones, etc... you get the idea! let the DM decide which gems he's got ready at any one time.
we might want to make it even less frequent than 1/day - after all, there *are* 333 of them, and he's got other powers besides...
That's true. I believe the official WotC method for writing 333/day is 'at will'
In reference to the AC and saves though, I was suggesting a continual effect, like bracers of armor, cloak of resistance and rings of protection.
EDIT:
I did some math. Using only creatures from the MM 3.5 of CR 21, these are the mechanics. The number in parentheses at the end is the average of the scores.
HP 370, 445, 459, 391, 432, 449, 387, 522 (432)
AC 38, 38, 39, 34, 37, 36, 38, 41 (38)
ATK 37, 41, 42, 39, 40, 40, 40, 45 (41)
FOR 28, 25, 26, 23, 25, 25, 23, 28 (26)
REF 13, 18, 19, 16, 18, 17, 17, 20 (17)
WILL 21, 23, 24, 23, 23, 23, 24, 24 (23)
Here are similar numbers from the Epic Level Handbook. It should be noted that although the scores are slightly lower, the creatures often have a wide range of immunity to special effects that makes saves not as important.
HP: 435, 405, 238, 562 (410)
AC: 39, 43, 42, 37 (40)
Atk: +39, +40, +39, +31 (37)
Fort +22, 24, 12, 28 (22)
Ref +22, 17, 16, 14 (17)
Will +17, 25, 12, 20 (19)