Nice that you are working on something for it Seb. Because last time you guys reaaally just gave up on it, but the engines (UE & ATLAS) you guys were working on were extremely limited and personally I can't think of a way how you could make the old node system work by doing things on just your end.
The old system could possibly have worked better if the ATLAS node system would let you put overlapping servers that handle the same information at the same time as the others. But ATLAS didn't really have the capabilities for this from what i've been able to see from it, so already there the easiest and most reliable way to fix the main problem with the old node system goes out the window.
The way I'd try to solve the old system would be using this overlapping by using "node crossing servers" for the node crossings. They would snap up the information of the character that is moving into the start of the overlapping area, hold on to it and preemptively transfer over that information to the corresponding server so that when the next server is taking over from the previous one you'd end up with a much shorter "node lag". These server/s would have these intermediate nodes as their one and only job so they could possibly manage a lot of these intermediate areas to decrease the total amount of increase in hardware requirement/stress.
Unsure if this would play out as good as I'd hope it would. But it also requires a different kind of flexibility with the servers and I know for a fact ATLAS sucked BALLS and i'm running on the assumption you guys were not allowed to touch the inner workings of it at all. Basically you guys sent them what you wanted them to change and then just hope they did something that worked for you. The overlapping system would effectively increase the amount of server nodes required for the same game world so thats the main problem with that idea on top of it being a tiny bit of extra stress on the normal play nodes as well. And this is just basically jury rigging the system instead of actually finding a better solution all together.