You have pretty much nailed it there. The fact that people have been racing to the core, and the fastest time to Sag A* is less than 9 hours, underlines how far from exploration we are. I wanted to be like Francis Drake (after whom my ship is named - or would be if they kept to that promise) or James Cook, boldly going where no one had been before. I don't even feel like Thomas Cook - at least he created excursion routes. Instead I feel like package holiday tourists with a "It's Sunday so this must be Athens" outlook.
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indeed... I know I have said this before so appologies for banging the same old drum, but imo when the thargoids come they need to implant a virus in all our computer systems and wipe out all our exploration data imo. The lore behind this would be they are getting worried we are getting close to discovering their home systems so want to destroy our ability to find them.
Further more they need to take down the entire nav beacon system. I would say keep the beacons there, but remove their ability to communicate with each other so we need to fly to them and connect to their data.
IMO we should then be all essentially in the black. The galmap being empty and then when we do a scan with the trumpet the only distant systems we pick up are systems that are in our jump range. (sure have some start on our gal map because we can see them after all, but there would be no way to plot a jump to them till we got suitably close to be able to plot said jump
When we fly to another system IF it has a nav beakon, if we fly there and connect to it, and download data from it, it could then show us the location of any stations in the system.
Further more, I do not think it would be that much of a stretch to add into lore that tidal masses affect hyperpace, so to plot the most efficient jump you need as much data as possible, therefore selling fully scanned system data to universal cartographics would be worth more money as people would pay more for complete jump data which makes it more fuel efficient.
Personally i would go 1 step further and make it so you get a (tiny) amount of ship damage for jumping to a system not fully scanned (because your jump plots would be out a little bit).
Not a huge amount of damage, just enough to mean we cant just plot a route to the centre of the galaxy. It would force us to expand slowly, fully scanning as we go, then returning back and selling the data.
"jump data" - separate from economical data - would be sold in grid fashion, so I would not buy a single system of jump data but an entire 3D grid of an area. this would also then show me where was fully explored as well as the fringes so i would know where to go to to explore.
To keep the 1st explorers happy from the existing set up, you could keep their names on when they are found again if you wanted (though me, i would be tempted to wipe the job lot but to give every pilot in the game who had fount a unique system a 1 off explorer skin for a ship of their choice.