Hmm most speakers worth consideration should go down below say 100hz.
Not to say one couldn’t explore a three box external crossover solution somehow. Could be an interesting if not very practical approach if done well.
Something different maybe. Any speaker vendors sell such a pre-integrated design out of the box? Practically I’d prefer to handle large heavy speakers in three parts of even two rather than one big heavy thing that is impossible to handle practically.
For example with my big Ohm F5s, the drivers are all self contained in a “can” that detaches from the cabinet “base” making overall shipping and handling much easier than most of comparable size and weight. Very unique !