Well, speakerdoctor, you and I are people who love this hobby and actually build stuff!
I must have built every combination of drivers under the sun over the years. Little ones and big ones. Simple filters and complex ones. We are really in the business of putting old heads on young shoulders.
Let's have a look at a variant of the SEAS Njord idea, the WLM La Scala.
6moons audio reviews: WLM La Scala
You might think the big box on the left is a good idea. But, TBH, only if you have a room the size of an aircraft hanger. Otherwise the smaller box will work better, because a small closed room makes the bass boomy. It's called room gain.
If I am honest, a three way works much better at every level with the same SEAS CA22RNX bass :
SEAS-3-Way-Classic
But since this our lovely hobby, I encourage relative noobs to have a go. You will get good sounds if you have a good idea. I still enjoy reducing the bass coil, and increasing the bass shunt capacitor proportionately. Part of my hobby.