Ok so 2.0 is released, I have the game installed and I just read some description from one of Aragorns new retinues. It seems you must capture Hoarwell, Tharbad and Coldfells to reunite Arnors old borders. After that you need to "restore" (aka build) the House of Kings in Annúminas. Last but not least you need to secure an alliance with Gondor and thus have them accept Aragorn as the Arnorian king.
Step 1: Capture Hoarwell, Tharbad and Coldfells while retaining control of your starter settlements.
Step 2: Build the House of Kings in Annúminas (Requires a large city, best way to achieve this fast is to use Aragorn as a governor in Annúminas and set taxes to low)
Step 3: Secure an alliance with Gondor
(Note; it seems you can complete these steps in any order but these are probably the most "natural" if you wish to roleplay)
This thread will be the basis for all the discussions regarding Arnor and it's reemergence. Hopefully people will see this thread on the mainpage and not feel the urge to create a new thread regarding this topic every day.
P.S. If you want a new color and name for Arnor once it's forged e.g. "Arnor" instead of "Free people of Eriador" Ayleid has kindly enough edited some files to implement those features. His post is on page 3.
There is also a submod for it that allows you to switch betweeen Eriador and Arnor color/names and vice versa. Found here: