OK, I'll do my best to explain.
I'll explain from my background. Orban offers Band 2 > Band 1 coupling. Band 3 > Band 4 coupling, and Band 4 > 5 coupling settings. This is what I'm used to so it's what I expect. Here's how it works.
When a band is coupled TO (1, 4, or 5), that band can never have less gain reduction than the band it is coupled FROM. But it *is* allowed to have MORE gain reduction. The idea in the case of Band 4 > Band 5 is to basically turn bands 4 and 5 into a unified band with the additional feature of a sibilance reduction feature in band 5. It is rare to have a song which would have much more energy in bands 1 and 5 than 2 and 4, respectively. But if that happens, we want 1 and 5 to do as much extra GR as necessary. The inverse is NOT true. Because bands 1 and 5 represent the extreme ends of the spectrum, we don't really want them to get any more dense than they already are. In particular, a very dense band 5 is bad on FM, and a dense band 1 gives a nasty rumble and puts a lot of extra energy into the final clipper.
Now, that doesn't mean you have to do it exactly the same way. If there is a better approach, that's fine. You asked what I expected, so I'm telling you.
I should note than in the Optimod 8200, what I described isn't exactly true (but it is in all subsequent Optimods). In the 8200, the gains of bands 4 and 5 were precisely identical with the exception of limiting. The other bands' coupling worked as I described above.
In no case, is there ever interaction between coupling and limiters for their respective bands (that I am aware of).