I had suspected it wasn't the best idea.
I'm with tomt, i think it's a great idea. The challenge is how to make it work and overcome the known, and to be encountered, caveats.

Great ideas are where innovation is born.

Once upon a time some fella got the notion that it'd be a good idea to run the HF transducer right smack through the center of the woofer. That went pretty well for Altec, eh?

Look where Tom Danley has taken his company in little over a decade with his intense R & D on co-entrant(synergy) horns.

If it was easy, everybody would do it.