It's entirely possible to get top result in every single major vote and all except one best result in minor issues with Kerannii and still be able to open Ruins before Erosian War. For example, you may go by Fulminato's MinMax route and tweak it in places.
At the end of Third Arclentian War you can skip Tak'kan Trade, delay Mushroom Farm and instead invest in Theltiar Rentals and Gasm Falls Trade.
After meeting Megail, swap War Monument and Succubus Band with Yhilin Bank, Booze Shack, Mercenary Office and Tradesmasher and you have enough social for Luanell and sufficiently more money. After Succession crisis you need to take Cee'kan shipping, Airships and most if not all cheaper profitable investments (Pillars, Weapon Store, Flowhouse, Mushrooms, Givini Smithing, Hall of Mental Strenght, Armorer, Band Tour). Orc-sculptor will give additional Tak'kan point for overwhelming voting. Also, you need to donate warehouse artifact to New Givini for additional 50k ProN from Orc Merchant.
After that you will have enough income to invest in Lustlord Temples, Succubus Tower, War Monument, Aram Eustrin Embassy and, later, Tak'kan Mine and still have just enough money to raise base defences, open Ruins before War and fully invest in Kyongan with major win in Mercantile issue.
All this investments, fully researched Sex-Purity magic before the Council, relevant RP scores and allies (Ignias, Jhenno, Kalant, etc) and Yelarel's light reforms, will give you ability to maximize Gawnfall while making a deal with Kerannii.
As a bonus you can more or less safely invest in Airship Militarization and Givini Mage Guild right after the Erosian War, which will give you everything you need for the Incubus War.
On the other hand unless you have practically all (except Givini Tunnels) relevant investments, overall top relevant RP scores, asked Hester for acceptance and directed Jhenno against Unification, you will have to sacrifice something, and the less you have the increasingly more you sacrifice with Kerannii.
But it can still be viable option to skip Lustlord Temple Expansion, obtain more Hester score (Shape the World choice) and save loads of influence, if you are ready to take average victory in Succubi acceptance vote. As I see it, the only noticable downside here is missing one more Vhala's RP in addition to one already missed due to not taking Esmera's deal and refusing her before Unpeople vote.