another suggestion

[gragamfor]

Could there be some pins to mark a domain on the map. Like yellow color for allies.
They can be researchable, 1 pin, 3 pins 5 pins

[Kennoway]

No such science,but I know there is a kind of scroll which can display what you want to see.
The scroll is named scroll connection with allies,it's not a rare scroll at all,i got two from ruins so far,and sometimes I saw it in the trader of my vault.