Joseph: I hope you don’t actually not know about the differences with Chabad mikvehs and that the question was purely academic. We can NOT be yotzei on Chabad Mikvehs, I heard even b’dieved, but maybe it’s possible to get a heter in some situation. The holes in Chabad mikvehs are on the floor; the natural water is underneath instead of beside. The logic is exactly as Chabadshlucha described above. I struggle to see how making a new mikveh design different from that used for centuries “avoids issues” though.
P.S. To straddle the line and make everyone mad at me like I always do: I think people are being a little hard on Chabadshlucha. I don’t think she meant to be arrogant in saying she wouldn’t quote non-Chabad rabbis. Just like we don’t cherry pick minhagim at our leisure, they also stick to their’s. Chabad takes it a bit further with the concept of being “bittul to the Rebbe,” which seems to imply that they don’t learn any Torah by which they don’t hold; they only lean shittahs that they would apply practically. It would be like saying “I only learn Mishnah Berurah and no other commentaries because it’s what I hold to be halachah l’maseh.” It’s a foreign concept to Litvaks, but I doubt they’re the only Chassidim with this approach. Do you really think Belzers, Satmars, Bobovers, etc would quote HaRav Eliyashiv either?