Do you mean as and when a particular player looks at a system map? That would work, but still relies on players knowing which systems they tagged so they can open the local map and update the local database.
If you mean automatically, then it would have the same initial problem of accessing the FD databases. As I understand it the only time the "first discovery" data is looked up is when a player opens a system map. To build up a local database of discoveries would require a client to simulate the opening of 400 billion system maps to see whether the current player had any tags in them. At one map per second that would take 12 years. Per player.
Unless there is a reverse lookup feature in the database(s) that wasn't explicit from the
relevant part of the AWS video, there may not be a way around this.
(The key to this whole thing is the S3 database referenced here:
If it's possible to search that on the "cmdrname" field then we're golden and it's just a question of waiting for FD to implement the code in the game. But if, as I interpreted the video, those values can only be obtained if you already know the system name, then we'd have to look up every system which is impractical.)
The easiest way to store a local database on the player's machine going forward would be to parse the "CONGRATULATIONS CMDR {name} YOU ARE FIRST TO DISCOVER..." pop-ups that appear when you sell the data, which is something I and no doubt many others currently do manually with good old pen and paper, or a spreadsheet. But that would still have the problem of only working for systems discovered after the feature was implemented.
I hope I'm wrong on all of this and there's an easy way for FD to implement an historical lookup of tagged systems, but I can't help but feel that if it was possible to do this it would have been done already. Then again that could be said of a great many things in this game that did eventually materialise, so maybe there's hope.