IMO, i don't think Erinmore, Firedancer and MacB Vanilla are high in nic at all. Royal yacht is definitely a step up from the latter 3, but certainly no stronger (if not less strong) than a full bodied habano/oscuro maduro cigar. Based on your OP, it sounds like you have a DAMN high tolerance for Lady N, which is the same with me, although sounds like you got me beat!
I would suggest, as Cosmic did, any of the flavored ropes. G&H make some fantastic examples such as rum, maple, coconut and sweet whiskey to name a few. They are pretty heavy in the nic department and taste delicious, offering a very full bodied and thick smoke. Hell, you can even chew the stuff if you get the itch. Have you only smoked Aro's or have you experimented around with different types of pipe tobacco? From my experience, Aro's and nicotine go together about as well as oil and water the majority of the time. Lakeland style casings added to flake tobacco or ropes aren't really aromatics and i wouldn't classify them as such. Just my 2 cents, take it for what it's worth. I hope you find some of this advice from myself and others helpful and it leads to you finding a new favorite(s).
Here is a link to some G&H ropes that might be of interest on one of our site sponsors website:
http://www.smokingpipes.com/tobacco/by-maker/gawith-hoggarth/bulk/index.cfm?tag=Rope