A guerilla? If you mean in terms of warfare idk, I only know partially of what it means... How about an explanation?
A guerrilla is a fighter who uses tactics that include hit and run, ambush, and minor scale battles. These tactics are often used in the afghan mountains. In fact, the first well documented guerillas were persian nobles from afghanistan who were conquered by Alexander III. A gorilla is an animal. He must mean the units in this faction would be quite weak as far as armor and HP goes, but would be fast at moving and attacking, and may take less longer and take less resources to produce. Since flanking (getting extra hit points by hitting a unit on it's back) is not implemented, this faction would be restricted to swarming, and a whole faction (even a mini-faction) of units that swarm is lame. So here is where a curiously advanced knowledge of herbs and berries in medicine (supposed to have been possessed by stone age peoples, especially Neolithic ones such as the North American plains and woodland indians, i.e. sioux, iroquois, others) for a medicine man that would heal units very well, and also a variety of heavy land units, would come in handy to balance this out with magitech.
Wooden darts were known at least since the Middle Paleolithic (Schöningen, Torralba, Clacton-on-Sea and Kalambo Falls). While the atlatl is capable of casting a dart well over 100 meters, it is most accurately used at distances of 20 meters or less. Seven spears were found in the Schöningen 13 II-4 layer, dating from about 400,000 years ago and thought to represent activities of Homo heidelbergensis. The atlatl is believed to have been in use by Homo sapiens since the Upper Paleolithic (c. 30,000 BC). Most stratified European finds come from the Magdalenian (late upper Palaeolithic). In this period, elaborate pieces, often in the form of animals, are common. The earliest known example is a 27,000 year-old atlatl made of reindeer antler and found in France.
The atlatl is a very basic and widespread weapon. It was used in many variations including ones in the North american plains region, Mesoamerica (the aztecs), and regions in the Eurasian landmass. It is a great idea for a unit, but I think it should not only require an upgrade, but should be a promotion from a spear thrower, which would have been a promotion of a spear stabber warrior. Great idea!
Off topic about Atlatls: I went to a place in South Dakota where some people excavated a whole area and found artifacts. They also had these atlatls that we were allowed to shoot. It is really cool and easy, except ours would sail through the air like mad because the darts were made out of curved bamboo. But the point is I can give you a real reconstruction of how it is thrown, if the youtube videos of them are not enough.
The Ice Age people are yes from the north, but not norsemen or vikings. I would rather stick to prehistoric because there are only a few mods or none about pre historic.
So this would be like an inuit/ice agers mod? That really would work because the concept is so solid.
So what is your point here? Are you suggesting that the units run when they are getting owned?
That would be a really hard tactic to master, even harder than orchestrating a pitched battle. I would like to think that this faction could include more ranged units because in those times, a very primitive melee weapon was not preferable to a ranged one that would do the same damage, but at least with the ranged one the guy wouldn't have to get up close to do the same damage... You just gotta keep it balanced. Try everything.