My character is the son of Odin, and another guy is the son of Ymir (Odin's grandfather). My Contacts and Resources skill should let me bring them into battle when neccessary, which it will be (the game is -18 refresh).
So, you are basically doing the "hiring" aspect instead of the find/create/become side of things, correct?
In any case, there are two things to remember: Every Einherjar is different, and the age of the Einherjar will matter. And also note that the Einherjar were warriors in the first place, so whatever they had before their death should carry over (to a point, of course; I don't think many Knights of the Cross would be Chosen and become Einherjar).
In the build I would use, a "new" Einherjar (from the 1900's-today) should have that aforementioned Mythic Recovery approach (i.e. recover from anything while in "Valhalla" or with the aid of a Valkyrie), and above average Discipline, Conviction, Endurance, and the combat skill(s) of their choice. At most, I'd tack on more Inhuman power on top of whatever else they may have.
Older Einherjar would be like wine and get better with age. The might get better with their preferred combat methods, but it is hard when you were already considered one of the best. Instead, I can see them "evolving" their methods of combat, especially
after seeing that museum-like armory in Changes, where Harry saw an evolution in combat methods, starting from old spears, moving through black powder muskets and grenades, and into super-advanced military equipment
. Give them the same Mythic Recovery, perhaps add on a Toughness power without the same Catch, and have no less than one Inhuman power onto the list.
Again, just my thoughts, do with them as you will.