Unfortunately, i don't think Madness is well-suited to DnD (at least the way it's been implemented). In the Granddaddy of all madness-based RPGs, Call of Cthulhu, one's Sanity plays an integral and fundamental part of the entire game. It's slow, gradual, insidious, inevitable and hard to get rid of, and that's all part of the horror that the system is based on.
In Season Three here, tho, it's tacked on, fast and blatant. AL wasn't designed to handle insanity from the get-go, and it's more a sputtering faucet in terms of effect. You either have a momentary pause in the module (short-term) a potentially module-crippling bout lasting for hours or tens of hours (intermediate) or a vaguely-debilitating "permanent" issue that lasts exactly as long as it takes for the module to be over and you pay for a spell to get rid of it. It's more of an extreme, ham-fisted environmental hazard that was shoehorned in, rather than a character-driven, slow, creeping descent into madness.
Not saying that it's not an interesting or intriguing concept to be incorporated into a D&D campaign, or even that it doesn't fit well with the Underdark. Just that I don't think it's necessarily a good fit for AL.