More ancient weapons.

[Homocommando]

In that period of time people used also weapons like atlatl, rabbit sticks/throwing sticks, slings.
Not sure about Finland, but atlatl is great, especially for bigger animals or spear fishing, and quite easy to build, so I think they must have used it.
Rabbit stick is powerful weapon, useful for hunting small game, and it is even used to this day by aboriginal australians (boomerangs).
Slings are not very accurate, but they are powerful blunt weapons, and you can just find ammunition for it on the ground.
I think it would be cool to see these weapons in game.

[Galgana]

Stonelobber's Primitive World mod adds rabbit sticks and slings.

[trowftd]

I don't think atlatl stood around that long in Finland, considering they already have iron broad heads and all kind of bows tells me that they probably have forgotten it already. It is only the Aztecs and Australian aborigines that used it till the modern times if I'm not mistaken.
I did not do any research on this but slings should be around that time considering at least the northern tribes were animal herders all the populations that have done herding are known to use it. Modding the sling is actually pretty decent, primitive world mod is good I would also recommend it.

[Homocommando]

Tamils also used atlatls until 19th century.
Some african, and filipino tribes use it to this day too. And I think eskimos use it for fishing as well.
Atlatls are even better than bow for hunting very big animals, and we do have in game a culture of strong hunters, who hunt big animals, so even if it didn't remain in real world Finland until this time period, it would make sense if it remained in UnReal world Finland.
Also atlatls surely do make much more sense, than bastard swords, for this time period.

[trowftd]

Oh yes, of course the atlatl was better for hunting big animals. But after the mega animals have died off slowly, bow was able to creep up to the top over atlatl. Maybe iron age Finns used it for elk hunting or animals that are similar size I don't know about that one. The reason I said this was because the Finns were not living purely as hunter-gatherers, so it seems a lot rarer to see atlatls in settled societies.

But disregarding all that, I would be pretty hyped if I were to see atlatls added into the game.

[Privateer]

 A quick search and translate netted me this:

 "There is no evidence of the use of the levers in Finland."
https://fi.wikipedia.org/wiki/Vipukeih%C3%A4s

[JP_Finn]

I can’t be the only one to use staves as rabbit sticks. Even the ingame encyclopedia states they’re about 3’ long*. “That’s not a quarter staff you got there son”
Throw it at a target, it’s spun the same as rabbit stick. Not lobbed as a javelin.

It would be nice to rename the the staff as rabbit stick and add actual quarterstaves in-game.

*with some crafting magic, they can be made into 5’ or so javelins.

[Homocommando]

Lack of evidence doesn't mean it wasn't used. Atlatls were easy to make and powerful, and they were used pretty much everywhere, so I am pretty sure at some point they were used in Finland, and as I already said even if they don't really match iron age Finland, they fit better than bastard swords, or two handed swords.

[JP_Finn]

There’s also no evidence that ancient Finns used phalanx formations and carried a heavy sarissa. Yet the technology existed for it, just the same spear head on twice as long shaft.  Should that be added too? 

If there were any levers/spear throwers, you’d think that it’d been mentioned in the folklore. Yet, I don’t recall a single mention of one.

[JP_Finn]

As for two handed swords, earliest mention of them (2-handers) that I’m aware is Thracian sempaia, which reportedly was strong enough to defeat Roman armor. (Armor here is likely hastati chainmail). Circa 400BCE
Another early record is Alexander the Great battling in India where they utilized “broad 2 handed swords”, these likely were large khukri/kukri up to 60cm/2’ blade length. Around 320BCE

It’s true, steel 2-handed swords started to appear, in Europe, 1200+ CE and is after the Iron Age ended in Finland.

[Matti-patti]

A casual look at Oakeshott type XIIs seems to indicate some longer bladed swords did exist in the period, they at least belong as much here as mail mittens/leggings and kneecops and coudes. I would kill the battlesword as anachronistic though, make bastard sword the big sword (though I hate the name, I'd use great or long sword) and buff it with +1 edge damage to make up for removal of battlesword (I'd also cut the weight of bastard sword by a pound).

While atlatls weren't used as throwing aids in historical Europe, leather straps (called amentum by the ancient Greeks) were used for same purpose in antiquity at least. The wiki page states they have been found in 200–450 CE Danish bog finds. Barely plausible I suppose?