The electronics would have to be different (more powerful) too. I like the idea of a Rebel in an AAA form factor, but brand P has made a few other lights in that spirit, and it seems to me that they've never done that good a job with the electronics, so I don't have good reason to expect it to be different this time.
It would be nice if Arc made one, but again, it's quite a departure from the classic low powered Arc AAA. At the end of the day I wonder what the purpose is. I think it would be better with 2 levels, which is more complexity. I have several lights of this type right now: the older and clunkier brand P 1aaa titanium model that I never use and don't really like, one from brand F (1 level Luxeon model modded by datiled with a Seoul) which is nice but whose led is less efficient than the latest ones, and the current brand F 3 level model in stainless steel, which I like a lot and carry most days, but which is a different concept than a Rebel-powered Arc AAA. I like the purity of 1-level lights, but for a high powered light running on a dinky aaa cell, practicality calls for a low level being available. So there is a dilemma. (I do think 2 levels is better than 3).
One approach to this would be make a Rebel board for the titanium Arc AAA, that interchanges with the other boards for that light. I'd certainly give it consideration. I do expect to buy one of those ti lights sooner or later, I just have reluctant wallet syndrome these days.
One benefit of a Rebel could just be better tint at low power. The Nichia tint is just awful once you've gotten used to more neutral leds. The Arc AAA Snow tried to address that, but I think never got traction because of beam artifacts, scarcity, concern over phosphor longevity, and that its tint was (while a huge improvement over the Nichias) still not all that great compared to the best power-leds.