I give you
Great Britain, Holy Roman Emperor, Protector of Europe, Bane of the Turk
So I started this game off just wanting to give the Hundred Years War a try, and it's enjoyable in a lot of the same ways that pre-nerf Byzantium was (before we started having to reroll 20 times for a viable start), only better because it's not as deterministic. You start in an unenviable position, but with a strategic advantage that can be leveraged to deal a lot of damage to the enemy, and a big payoff if you do. You don't have as many degrees of freedom in terms of where to go from there, but taking over the HRE diplomatically while conquering Iberia militarily turned out to be a lot of fun.
It was a remarkably unlucky game. My only preplanned goal was to win the HYW and take over the HRE, which I finished in 1644. My original 0/0/0 king lived to well into the 1480s, which screwed my whole idea schedule and put me behind in colonization, which put me behind in everything. He had a late heir, so when he died I got the Low Fertility event in 1498(!) because the new heir didn't have an immediate new heir, then War of the Roses, which I won for Lancaster. After that, I had some wars with Burgundy for Antwerpen, and with Spain for Iberian provinces. As usual, I didn't integrate France until 1750 (to prevent Rev. France) so I could enjoy their god-generals and their AI-controlled sieging, which made big wars very enjoyable from the get-go.
Castille/Aragon had both set me as a rival and Portugal sided with them over me, so we were about evenly matched from about 1450-1650. Vizcaya must have changed hands at least four times. Castille got the Iberian Wedding event, but I managed to break the PU with Naples, at least. Iberia would end up occupying me for the entire game due to not getting a single PU until 1750. That one PU was with Georgia, and it ended six days after I got it, when they got the Bureaucratic Despotism event. This was incredibly widespread, actually: by the end of the game, Sweden, Byzantium, Ottomans, Russia, Poland and Portugal had that form of government. So, so many throne claim opinion maluses for nothing.
I decided to ally with Byzantium early on to keep it interesting, but they had already lost Constantinople and were just hanging out on Cyprus and Crete, so they were relatively passive even after I gave them back Morea. In my Portugal->HRE game, allying Byzantium was a constant source of fun as they would keep attacking the Ottomans despite being much smaller, then call me in to lay down the law. This game, they just sat there, so I ended up diplo-vassalizing them.
I also own all of North America, but who cares.
And the HRE map:
That's East Frisia up there holding out against the Empire. I originally released them for IA without noticing they weren't actually in the HRE, and I didn't incorporate them because they were such a fierce little OPM. Over the span of about 175 years, OPM East Frisia fended off
six Swedish attempts to reconquer their core, during four of which they were facing a Sweden that held all of Scandinavia. I don't know how they did it, but hats off to them--every time I saw the war declaration, I thought this would be the time I would retake them from Sweden and put them in the Empire proper. I think Asterix may have lived there.
Note that I did force that jerk the Pope into the HRE, though. My only regrets are not managing to evict the Ottomans from Europe entirely, and not managing to time my annexation of Pomerania right so I could surround the HRE on all land fronts.