Considering GalCiv's history, you'd think that everyone here would want Cultural Conquest to be a difficult victory to achieve. As long as a lone starbase in an otherwise empty sector of a gigantic starmap is still using ancient, unsupported software to run the bots in their loading bay, Cultural Conquest should be an impossibility. You'd either have to convince that starbase to "upgrade" its software (sell your culture), build a bigger starbase in that sector (assert your own culture), or blow the sucker away (eliminate the opposing culture).
I'd like the criteria for Cultural Conquest to involve a combination of conditions:
1) Possession of either a certain number or percentage of cultural wonders (Ultra Chocolate, et al). Other cultures must want your goods (in game terms), it isn't enough to flood the market with cardboard hamburgers and fries laced with opiates - that’s Commercial Conquest.
2) All other cultures must have at least "Warm" ties to your culture. This would mean that how you gained your influence in a sector wouldn't matter. Destroying an aggressive culture could still win you points from other cultures and pockets of resistance could still oppose the “Insidious Galactic Conspiracy (tm)”. Just like the real world.
3) A "bare majority" of influence in every sector. That is, having at least 1% more influence than any other culture in a sector, rather than having a "controlling majority" of influence, where your culture's influence is greater than the total of all other cultures' influence in that sector.
I think I'd rather have influence work this way anyway - if you don't have the "controlling majority" of influence in a sector, then that sector is still up for grabs and is displayed as “uncontrolled”.
This would also serve to conceal the slippery slope of cultural invasion. No single culture appears to have cultural dominance of a sector, but you can buy blue jeans on every planet and starbase, and every culture in the sector is trying to create its own boy band. For those of us who are sloppy micro-managers, you could provide a pre-game choice of being warned about covert forms of conquest.
Speaking of which: is there an option to win through espionage? There’s not much sense morphing a few of your own Drengins if they don’t look remarkably like the Drengin High Command.
I think Cultural Conquest should be significantly tougher to achieve than Commercial, Diplomatic, or Martial Conquest.
Finally, would it be possible or desirable to set the victory conditions at the (possible) end of the game?
Say that you've met the conditions to win the game by Cultural Conquest, but you've got your heart set on achieving Tech-Nirvana. At this point, a dialogue box pops up and you're asked whether you want to keep playing. Or, the United Planets could assemble to vote on crowning a Galactic Emperor and there are only two choices on the ballot - Terrans or “You can't become king just because some watery tart lobs a scimitar at you!” You could also do this for Commercial and Diplomatic victories (for those of us who just want to keep playing until all the pixels are Terran Blue). Does it matter when the victory conditions are set for the purposes of calculating your score?
End transmission.