Suggestion, for now, can you add a symbol or indicator (locked symbol maybe) to all the not conquerable location so people can easily know and you can guide people easier if they don't understand.
As a solo dev on a weekly upload schedule I honestly can't take the time to create assets and code that I'm just going to remove later. Besides, even if I did, the messages would just turn into "how do I unlock the territories with the lock icons!?" ;P