The Mass Storage thing is a vanilla Issue, its just that vanilla does not make actual use of the exact coordinates that have been clicked (except when placing Slabs, but that’s Y-Axis only) so it’s invisible to players.
This issue indeed is a floating point problem, the thing with that is, that I cannot use double instead of float because it is vanilla itself that provides the coordinates as float to my mod, so I cannot change or fix the Issue…
As for the Grid shifting, that MIGHT be fixable, however that might be problematic since the Grid probably shifts into the direction that the expected Coordinates shift to, and since I cannot fix the expected Coordinates, I cant just fix the Grid…
Sorry but this is sadly a wont fix for me, since I cant really do anything about it…
Also there is no real reason to ever go into the Millions with Coordinates, at that point you could just host multiple Servers or use Singleplayer and even get better performance. Or use a Dimension Mod that adds more Overworlds so that each player gets one. Or split up the world in four along the X and Z Axis and tell people to not build across the borders, this goes well if you enable the Center Streets of GT6 in the Worldgen Config. ^^