We were researching Divine Right as Trader Bait, but, honestly, I'm not sure how many other nations are even willing to trade with us. Ragnar is a fairly significant tech lead at the moment, but nothing especially critical, save Engineering. He can field: Berserkers (Macemen), Catapults, Trebuchets, Crossbowmen, Longbowmen, Pikemen, Knights.
We can field all of the above except for Pikemen and Trebuchets. Finding a way to acquire Engineering would be wise, although Ragnar's army (as depicted in the last image) seems to be Infantry heavy, so it may not be desperate. Crossbowmen + Macemen would still be a good combination, plus a healthy dose of siege units (catapults).
In any case, yes, Ireland is not a major objective, and an immediate attack on them would be foolish, even if the Vikings were happy with us.
One other thing we should consider doing is sending out a cheap 2-move unit to explore more of the world, since our maps are woefully inadequate.
Now that the war and negotiations are over, I'll begin working on The Plan. I'll still need a few days, of course.
Edit: Great General settled in Birmingham (HE) is a good idea. I'll do some math to see whether Longbows or Crossbowmen would be better. Antium can be a troop producer, as well.
However, if we're not giving cities to the Vikings, we're not giving any more to Germany. Those cities are worth MUCH more to us if we control them than if we give them to our vassal. We can defend them ourselves.