I think a cool new addition to the game would be to add 1 way connections during mapmaking. This could be especially helpfull for diplomacy maps.

For example, you can't attack sea tiles from territories without a port, but you can invade thst land via a sea tile.
Or I guess a specific mountainpass you can only force your way through via one side.

I'm no programmer but it sounds like a relatively easy addition which would give mapmakers alot more options.

There is already a mod for that

WHAT?!