According to jtorr :
Yes, you're right.
It wasn't evident when I initially looked at it on paper with 2 of the
5 needed switches.
Once you add the 3rd, a loop is created such that no matter what the
position of those 3-way dimmers, the lights would never go out.

So, redesigning my original idea, instead of wiring the junction box
between the 4-way switch and the 5 3-way switches, I think I'll place
the junction box after the 2nd 3-way switch and replace the 5 3-way
dimmers with plain dimmers (1 for each light bank).

So, the resulting circuit would be :
source - 3way - 4way - 3way - junction - 5 plain dimmers - 5 light
banks

Essentially the junction box would be spliting the common with all the
neutrals tied together.

Yup, that's the way to do it. Think of the 5 plain dimmers and
5 light banks as a single "device" fed with a _single_ switched hot and
ordinary neutral. The switched hot and ordinary neutral are supplied
by the inline string of 3-4-3 way switches.

Aka "divide and conquer" ;-)
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.