Not really read the thread but my own thoughts and ideas. Feel free to nick them off me Sandro, for I might have nicked them off others unwittingly...
The infinite ADS thing was really way too powerful for its own good. How to improve and balance it though? By breaking the process of scanning down to tiers of resolution according to distance and quality of scanning equipment and each with appropriate tiers of pay. There is precedence for newer things appearing with distance to a body, such as points of interest popping up when you get to below 1000Ls of them.
The idea is summed up hence:
Tier 1 - Discovery Scan ping, using the same ranges as before, giving locations of "blips" but not what, with a scanty monetary value
Tier 2 - System scan identification of blips (equivalent of current discovery scans but by moving to and scanning the blips)
Tier 3 - Surface Scanning at surface visual distance (equivalent of normal surface scanning now but closer range)
Tier 4 - Detailed Surface Scanning at surface visual distance (equivalent of Detailed Surface Scanning but closer range)
Tier 5 - Serial very-detailed surface mapping of the entire surface of an astronomical object according to exposure to the scanner
I think letting the Disco scanners pinpoint the existence of something out there would be useful, but to identify that something you need to fly up to it. Keep the ping ranges the same though. This is
Tier 1, and here objects appear as grid blanks on the system map and as a question mark on your target hologram.
How far do you fly up to those blips? Enough (with balancing) relative distance in accordance with mass to give a rough view of the object of the sort of resolution the ADS does now, maybe even to the distance normal scanning reaches at present. This is
Tier 2. At this point the object appears like it does following a disco ping nowadays on the system maps and target holograms, a localised equivalent of the pansystemic "honk" today.
Detailed scan? You'd need to fly even closer. Perhaps close enough for visual identification of the surfaces from your unenhanced eyeballs in the cockpit. Resolution depends on if you have a DSS (
Tier 4) or not (
Tier 3).
Even more detail? You'd need to be in orbit, and then perhaps engage in Very Detailed Surface Scans, and multiple at different parts of the globe, to cover the whole surface and pick out places of interest such as Thargoid structures or Guardian sites or geysers or abandoned camps or brain plants or whatever.
Tier 5, the surveyor's tier.
So what, you may ask. What would constitute a Discovery tag? Well, planetary body disco tags will still need the (detailed) surface scan level resolution of tier 3 and above. However, then if a Tier 5 scan picks out something interesting, then that surface landmark discovery is yours if you sell it.
Also, what about undiscovered bodies already with stations? The stations may have a limited amount of exploration data (no idea what their excuse is

) but the same rules can apply.
Payments? They scale to Tiers, but with Tier 5 you earn more by scanning more of the body surface, up to 100% of the surface. There are also survey bonuses for scanning and handing in complete data for a system (doesn't have to be all at one time but only if your data set for the system is complete according to your map and UC's records), bonuses for points of interest, and of course the individual First Discovery bonuses (but no bonus for getting ALL first discoveries in the system

).
But wait. There's more.
For then comes
Tier X, extra special close ups of points of interest and astronomical bodies. This is where your camera suite comes in. Unobstructed and clear pics of a feature can be carried with you and delivered like data to UC, but these are scrutinised by a real person on the other end and paid accordingly. Why, your contribution could even make it to Galnet, or the newsletter!
Next,
Tier Y, salvage of any interesting things, covered to some extent in 2.4 announcements under Salvage, but which could also spring a hidden mission on you - as could any of these things. Completing a mini mission could net an exotic reward of often priceless value -
Tier Z.
Oh, and the reason to nerf the discovery scanners' resolution? They emit so much radiation right now that the Thargoids hate it when you use them.
.....
Other ideas I think should be included:
Exploration black boxes - dropped when your ship blows up. Anybody can pick them up, and you can either hand them in by preserving the original discovery tags but keeping the money the lost Explorer should have got, or risk a pay cut by claiming the discoveries as your own (pay cut because UC will see the data is tampered with and "damaged"

).
EDIT - on second thoughts, the value of the black box would be identical to the value of the data within, including discovery tags - but as the data files are damaged, the maps cannot be updated and no discoveries can be apportioned to anybody from it. It may, however, spark rumours of things out there and even trigger a mission or community goal or three.
Spy missions! Building on the Tier X idea, bring back spy photography missions from Frontier Elite 2, but this time using your free camera on the camera suite. Picture quality and therefore reward depends on proximity to the target without getting caught and blown up (getting caught gets you a rep drop and pay cut for blowing your cover, getting blown up fails the mission for destroying your data). May or may not be linked to a subjective player/dev judge, we'll see.
And on a similar note, nature photography missions which are essentially missions to tourist hot-spots or natural features, which pay extra for spectacular images - and even may bring fame.
Dark System Limpets - launched from only the largest ships (the controller can only fit on class 7 and above), these highly advanced limpet drones scry the local witchspace waves and can search for and pinpoint dark systems, rogue planets without a primary star, etc. at a preset light year range. Note that excessive use of them may make Thargoids VERY upset...