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[alien space marine]

Could be a good idea, but then you argue 'why can't I conquer their territory and get production of those units myself'... :)

This could work... why not make the barbarians more of a real side? As it is they're so simple just attackers with bases. Which is not horrible but as the series progresses some more detail could be good. So implementing some aspects of more complexity for barbarians might work well. It'd be tougher to do something like you describe in BotF though because of how many nations and tribes there are, but they could have something with each tribe having differing levels of affinity to each possible player nation... complex but doable. So some tribes would more naturally fall into your sphere of influence and probably eventually turn into your own cities (before that trading and stuff), while others would resist as classic barbarian towns.

The number of such tribes should be controlled by the 'Barbarian Activity' slider, I think.

What do I want to see from Civ IV... hmm, the High Council in video form that interact with eachother, Wonder movies, a restricted Wonder list (seven per period is perfect. Perhaps if you still want Minor Wonders have an additional seven of them.), a better game interface (Civ III's isn't as good as Civ II's), a minimap in the map editor, scenarios from the start, a much better resource system, no way to not have any decent access to a river or lake from your starting town (for irrigation)... hmm... Oh, I also prefer Civ II's combat system. I like health bars over hit points.

1. If you conquere the Barbarian settlement , You wont get anything from its people , No Tech and no maps , No Gifts. Since you have just agressively annexed the city you just eliminated all males of fighting age so no special units. The only reason you should conquere them is if they are too savage and hostile to be reasoned with or too deny a rival world power.

A simple way of implementing it is following what CIV 3 added already with cultural straits , If you havent noticed when you pick your race they have a staus like Scientific ,industrial ,Militaristic,Religious,Exspansionist,Agricultural,Sea faring. Already each Civilization in the third game has two of the above types , The Barbarians would be the same , Warlike Barbarians might respect a warrior nation more then farmers and priests same goes with the rest.I can already see the Sea People as exspansionist sea faring people,As long as one strait is common with your civ and the barbarians you could be abled to trade and intergrate with them if not, They will mock you or be disinterested.

As for Wonders Big wonder more dramatic movies , Small minor ones you get the drift.

In conquests some of the wonders can give you exclusive rights to create a special unit , The Statue of Zeus lets you have Ancient Cavalry and You get Cruisaders for another one later on.