I'm not sure if some of the data can be cached in savefile to reduce the amount of time it takes to build cartographer map data on load. With a somewhat larger save file (can attach) it takes quite a while (30s-2 minutes depending on the time allocated in mod settings) to process the world after loading and start drawing the map.
I don't think this is anything high priority, and it may be on your ideas list already, but I figured I would share my 2 cents worth.
Thank you for such an awesome mod even if this feature request isn't worth it (of course you have limited time and probably many other projects as well)
@yeshjho