Troy is not something I'm particularly excited for, outside of the gorgeous and detailed map which can be used for some great mods (rise of Macedon, maybe...), and I won't lie that I would have preferred almost any other setting. Between the release of Thrones of Britannia and the announcement of Troy I'd been thinking of a few different ideas, keeping in mind the requirement that Saga games are generally supposed to be located in one specific region of the world and not being too large-scale (e.g. Japan for Fall of the Samurai, the British Isles for Thrones of Britannia, the Aegean Sea for Troy).
My first idea was the Great Northern War, which raged for a full 22 years between 1700 and 1722, and involved all the major players of Eastern and Northern Europe - Sweden, Denmark-Norway, Saxony, Poland-Lithuania, Russia, the Ottoman Empire. It's a "flash-point" in history (as CA describes the Saga titles as being) because had Sweden been victorious in the war, it's likely that they'd remain the greatest power in both Northern and Eastern Europe, and Russia would remain pretty much irrelevant and backwards. The whole political landscape of Europe would thus have been changed forever, even just if the Swedes had have been victorious at Poltava (1709). The map could stretch from the Gulf of Bothnia in the north to Crimea in the south; from Denmark in the west to Moscow in the east. The majority of the HRE will be fogged out since it is not relevant to the campaign. The playable factions would be Russia, Sweden, Prussia, the Ottoman Empire, Poland-Lithuania, Denmark-Norway, and the Crimean Khanate. Each would be pretty unique to each other, with some almost purely cavalry, Mongol-esque armies (e.g. the Crimean Khanate), while others are almost purely modern infantry and artillery (e.g. Sweden, Prussia). And of course the Winged Hussars will play a prominent role if you play as Poland-Lithuania. The campaign would be 12 turns per year, which, considering the war stretched for 22 years, would make the campaign 264 turns, a fairly long but not excessively so time.
The other idea I had was inspired by a book I'm reading at the moment called The Anarchy: The Relentless Rise of the British East India Company, which the name suggests what it's about. The campaign would include all of modern-day India, Bangladesh, and part of eastern Pakistan. It would begin in 1740, a few months following Nader Shah's sack of Dehli, which saw the fragmentation of the Mughal Empire and a general anarchy and chaos descend upon India. Very similarly to Three Kingdoms, the basic premise is that as an old and once-mighty empire begins to collapse, warlords try to carve out their own kingdoms and a few loyal governors try to restore order. Meanwhile the British and French trade companies along the coast see an opportunity to expand their holdings, while the rebellious Maratha Confederacy rampages across India, conquering vast swathes of land from anyone and everyone. It's honestly the perfect set-up for a Total War game. The unit and faction variety is enormous; from Persians in the east to the Marathas in the south and centre, to the Mughals in the north, to the Europeans in the west. The Europeans would have significantly less resources than their Indian enemies, but their troop quality is extremely high; they can also recruit sepoy units (i.e. local Indian soldiers). The Mughals and Marathas have predominantly cavalry armies which were fast and mobile but very vulnerable to gunpowder weapons, and the Persians have a deadly mixture of both. There would be a strong focus on diplomacy and political intrigue, as all factions form alliances and secret pacts to outmaneuver their enemies, and the European factions can hire out their armies to Indian factions - maintaining control of the army but having to follow the general orders of their Indian paymasters (a similar mechanic to the condotierri in EU4, for anyone that's played that). Again, the campaign would be 12 turns, spanning from 1740 to 1764 (the year the Seven Years War ended), for a total of 288 turns.
What are some ideas that you guys have?