I don't think you've explained this well enough. Does the drain stop if you hit a note below a certain %? (like the extended Stop Time on Panel de Pon when the stack is near the top) Or do you activate a drain stop using some trigger key?
Also keep in mind that the Easy mod already gives you three Kiai bar refills once it hits the bottom.
Oh whoops, should have said combo multiplier. So say if you miss, the combo multiplier does it usual speed drop to 0, but if you hit a beat, you can recover up to 25~50% of your multiplier, if you got back fast enough.
If it's unranked, your score is effectively zero anyway, so what's the point? If it's ranked, people will be spamming this for deathmaps they can't otherwise FC but would be otherwise useless.
Such a drastic change to the scoring system balance stands pretty much a nil chance of happening, so I feel confident denying this outright.