I think to make it really feel right you'd need to link it with the civil war, and have some effects there. Also, just as a kicker, Thalmor assassin organization.
I haven't tried it, but I've seen others who have, and I keep seeing the same response, that it can't be done. I would love to be proven wrong. Patrick Stewart is amazing, and he hasn't aged since Dune!!! That was 1984!!! https://i.pinimg.com/564x/a7/2b/b8/a72bb87c8658970bbc70f8536e3842a3.jpg
My own take is that they don't leave bodies rotting in the Valenwood and could care less about the rest of Tamriel. I'd check Hunterborn for the bone arrows and bow, but they can use wood from outside Valenwood like TaeRai said. Basically what you really want is some very meaty recipes. Look at Complete Alchemy and Cooking Overhaul and Hunterborn and I think you'll be 90% of the way there. That leaves the Spriggan thing, which is **much** harder.
I think part of it is that wagons can get buggy as they're moving. They horse is the actor and the wagon is just attached so there can be a lot of bounce. It's probably why they act as they do in game. The more wagons on the road the more often you'll see them being odd. Now a mod that adds carriages loading and unloading at farms and cities.....
This might dovetail into bandits that are begging for mercy, you could take them to jail, or the sneak skills where you can knock people out (if I remember correctly).
That's relatively easy, just tedious. You have to remove the magic items from the leveled lists, change quest rewards, change NPC spawns, probably change the spells to make them more powerful, longer cast times.... Good Luck!