I have been mulling this over some more, and assuming something is changed from what Frontier initially showed, I really feel as if a toggleable overlay is the only good option. Not just from a development standpoint, but also from a player standpoint.
Up until now, in game, the galaxy map has not really been leveraged for anything beyond individual systems. There was no in game reason for the galaxy as a whole to be divided up. That is changing. There are now game reasons for this.
Over the course of time, some players took it upon themselves to divide it up starting way back at the beginning, and those divisions have become generally accepted, I think in part because it didn't really have any impact beyond just giving a feeling of a neatly labeled and cool looking map, and flavoured descriptions when presenting expedition waypoints, or neat discoveries. The importance of that should not be understated.
That said however, my feeling on the current state of the Galactic Map naming is that it is pretty useless for actual useful navigation and quick reference. There is no convention in it at all. I am a longtime and fairly accomplished explorer, EDSM member, EDD user, been millions of light years all over the galaxy, spent a lot of time looking at the GMP, and to this day, would have no clue where the Angustia region is, and would have to essentially scan the map top to bottom, side to side until I found it.
What I would most liken the idea of this threads general proposal of having community named sectors, regions, what ever one wants to call them is a phenomena I see here in the USA of giving honorary names to sections of highways, bridges, residential subdivision roads. Where the honorary name of the road is not actually the road or bridge name that is used in an official capacity for route planning, 911 services, postal services etc. They are there to make a community feel good.
Thinking about naming of streets in cities and such, yes, there are lots of completely oddball things out there, but there is also a lot of convention that actually assists in navigation such as numerical names, alphabetical names that increase or decrease based upon direction. Presumably Frontier galactic sectors are going to have a quick and easy rhyme and reason to them so with little effort, if someone says Sector 37, players of all walks will be able to readily envision where in the galaxy is being talked about.