Ehh.. maybe it's just me.. but... your galaxy rotates... a static chart like this wouldn't be a major help. Maybe I'm missing the point though.
But the rotating does not change the assigned coordinate system. Why? Well the coordinates of your homestar are always the same....
As far as the wormhole thing, how do you know the positions are not random for each persons game?
Easy to find out. Go find any black hole you like and note down the coordinates of the hole you start and the hole you arrive. Also the names of the holes would be useful.
Then someone else checks that specific hole in their games and if the wormhole leads to the same destination it's save to assume the wormhole net are the same in every game (which I strongly believe).
btw: Be careful after wormhole jumps, the coordinates do not update (it still shows the coordinates you started from), glitch! To refresh them, jump to a nearby star and back to the hole again.