(I cannot believe that this thread is still alive.)
As for your last post hclass, in fact, you are not wrong. I think you are very right in that regard. And this is one of the things that I am looking forward to in Civ5--a more intelligent AI that is actually trying to win the game. I would assume (hope?) that if you uncheck everything but conquest victory, the AI will act accordingly. Thus I am really excited about the new AI with its three different levels of thinking (strategic, tactical, operational). Here's hoping that it lives up to the hype.
(Belive me, the Earth will still spin even if all of us have decided to end our life)
For the mentioned problem:
--- Solution 1 ----
Firaxis can solve the problem by puting victory of the same kind into a group. e.g. Dominant and Conquest as a group.
And a radio buttons is all it needs to make sure in every group at least one victory type is selected.
This should save Firaxis from modifying the AI (to make them looked aware of user's victory selection)
--- Solution 2 ----
Make AI with modifier in setting their character/attributes (which in the end determine what he/she will pursue)
Then based on what victory type user has enabled, 100% value is distributed equally to corresponding modifiers. (modifier of deselected victory receive zero value)
i.e. like my case, beause I select only "Conquest victory" 100% of value is added to the modifier of war/agressive, therefore making every AI player absolute warmonger.
---- Note: ----
It will take much less effort to solve by Solution 1 than 2, I would expect the lazy Firaxis will definitely choose 1, since they always seem to be lazy to me...
But I have heard about this thing called modifier in shaping leader's character in CIV5... (Could it have anything to do with what I have mentioned) I think Civ5 is going to be good. At least, this time the lazy Firaxis might have decided to choose a hardworking path... it at least sounds like a good news... modifier...modifier...modifier... O KA SAH KA!

O KA SAH KA!
--- My preferred solution ---
And the story never ends with that probably good news above, I have a better suggestion for Firaxis regarding the problem:
Just discard the victory type selection from the option page and make every player declare what he/she wants to pursue at the beginning of the game. Once decided, there is no turn back. So, all man know at the beginning what each want to fight with.