Well, what we ran into last time was the Holy Roman Empire banding together to take down those Western Tyrants Burgundy and Britain at various points, and then getting flattened by every other player at once, and then banding together with Burgundy and Muscovy(?) to try to slow down the wildly-out-of-control Britain. Honestly, I really liked the diplomacy, but it did slow down the carnage somewhat. What about a modification, wherein countries are only allowed to ally in groups that have a maximum size of the largest player? For example, Genoa, Netherlands, and Hamburg might form an alliance and still be smaller and less powerful than a well-off Burgundy or France.
The endgame was largely locked in stasis due to the Central Europe<-Austria<-GBR->Russia diplomatic scenario. Central Europe was bound into a permanent alliance due to their reduced size; GBR and Russia were unable to face them alone, and were consequently pushed into a similarly permanent alliance, whereas Austria, wary of an Anglo-Russian coalition, entered an alliance with GBR. The convoluted result was that, with war being incredibly logistically taxing for the two largest nations, and Central Europe being unable to face both simultaneously, player-on-player military action slowed down to a crawl.
That might have peaked into a war between an Anglo-Russian coalition and the HRE over de facto control of the balkans, but the aforementoed ties between Austria, GBR & Russia defused the situation. The overall diplomacy made for an entertaining game, though I don't look forward to trying to hold together a hybrid continental/colonial great power again in the near future. If anything, the game's non-scaling WE gain system was the greatest culprit in the eventual scarcity of open conflict; when you have 20 years of rebels to look forward to after a major war, you don't go to war with another player unless you are doing so to change the board's scales for good.