Delta recently posted "Wisdom as Sanity," touching on one of the items that was already in my ever-growing house rules project. The post and its ensuing discussion revealed a number of people had made the same judgment about tying sanity to this ability score. (Great minds, etc.)
My own feeling is that if your game calls for sanity rolls, it might be worth it to devote a corner of the character sheet to this mechanic. For my own use, I envision a saving throw for each sanity-challenging encounter, in which a failed save would be ticked off on the table below. The table is based on the modifier spread for B/X ability scores. Every time an entire line is ticked off, that point of Wisdom is lost.
This is probably more fiddly than Delta would prefer, but the possibility of losing Wisdom and the PC him/herself gives sanity checks and insanity teeth, and if it's worth having a separate mechanic for it, it should really make a difference in play is my thought. At the same time, I tried to come up with a mechanic that had a rationale but remained relatively simple.
Anyone is welcome to use or adapt this table if they so desire. (All I ask is
A final note: the special prey that this would make of clerics to sanity challenges has already been noted. It would make sense to me that a cleric who was currently under a Protection [from appropriate alignment] spell that protected her/him from attacks by the insanity-inducing creature would not need to make the saving throw for the encounter as long as the spell was in effect.