The mod is ready, please move to this discussion:
viewtopic.php?f=181&t=427585
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I start a new topic, because I've gone further in the project.
I am remaking the vanilla galaxy but instead of adding clusters, as other have already done (se no need of more), I am expanding the vanilla map INTERNALLY.
I don't exclude adding some more cluster but I think it will not be necessary
Indeed the vanilla layout is very limited in comparison with what one can do inside EACH cluster, not to mention that the connections and layouts look very casual
Simply speaking, I am remaking a galaxy more in the way Rebirth is, with more logical connections aka superhighways inside each cluster.
I also follow the same philosophy I used in my Farnham's Legacy MOD (see signature), which further expands the idea of having multiple sectors of the same planetary system (alpha, beta etc.) instead of random poetic names that don't follow any logical planetary layout
So now every cluster has at least two sectors, connected by highways. Here an early example (but I've done many more clusters already):

Btw after experimenting with added sectors, I found out an unexpected result, i.e. you can have more than only 3 sectors in each cluster
Here is new Grand Exchange:
https://i.ibb.co/DKPpMKB/grandexchange.jpg
I think this opens up a lot of opportunities to have sectors look as planetary systems. Maybe I'll go further and use more than only 2 sectors for each, will see...
Up to now I've already re-worked a lot of sectors, by moving planets (and redone in parallel with my other mod 'stars'), expecially new gas giants.
So not only a more logical layout, I also rework every cluster to look unique, not a bland one planet + one moon.
For instance in Second contact I added a gas giant and the planetoid is an earth-like moon orbiting it. So every sector either coincides with close orbit of a planetoid/moon or with a Lagrange point towards the central giant.
Using PARENTED multi-CLUSTERS is very nice because one can change the models for close or low orbit.
I move gates accordingly but also trying to make sectors have a role, so f.i. no more gates in the CORE ORBITAL sector! That thing really spoils immersion...gates are either in the Lagrange points or close to some moon, not in the low orbit of the main planet..

Also I am changing some gates into accelerators, in order to further expand the planetary system into proper multi-planet system (at least, if not a whole solar system).
I'd like to have more clusters redone in the way of Second Contact.
This mod pairs very well with my Engine's Mod (and with Stars Mod of course) because travel is managed by super-highways and there are NO highways. With the engine's mod, accelerations are not instantaneous as in vanilla, travel too is longer. So Sectors literally EXPAND even if I don't move things apart, because travel time is longer, not the distances