Skyrim has mods.
This has the potential to become an interesting problem for the game industry. On the one hand, Bethesda is one of the companies that strongly supports the modding community, releasing the Creation Kit for anyone to try their hand at adding new content, changes in focus, or basic bug fixes to the worlds of Skyrim and the Fallout series. This, when it works well, gives games some of the advantage of Open Source. There are some very skilled people out there who don't happen to be working for Bethesda (or who don't have any deadlines other than self-imposed ones) and are able to do things the original creators did not or could not.
On the flip side, official DLC can look bad by comparison. I have to say that Bethesda shot themselves in the foot a bit with Skyrim, at least. The two big DLC's, Dawnguard and Dragonborn, got decent reviews and are considered more-or-less worth the price. However, Hearthfire is considered by most reviewers to be a waste of money, hence a waste of employee hours by Bethesda (unless they got a lot of sucker sales).
Skyrim SE is even worse. It appears to have made back the money, and even has a trickle-down on the modding community as it brought a crop of new and returning players. But what it delivers is basically not worth it; it is nothing but a simple graphics buff that is outdone by existing free mods in both quality and functionality (as in, delivering spiffier graphics without causing the frame rate to drop through the floor.) It also offers no expansion to play and doesn't fix any of the known bugs.
Although I have to say, as an aside, dealing with bugs is part of the Skyrim experience. Some of them are left in there because they actually add to play, such as the ability to ride a horse up a vertical cliff, or the ability of a Giant to club you into low orbit. As long as they don't completely break the game, an exploit is fun; it really depends on whether you find it more fun to crawl through twenty Ancient Nord ruins in search of loot, or sit down at a pair of crafting stations swapping bottles of potion and enchanted jewelry in the circular skills buffing exploit.
My Breton Archmage with near-legendary Alchemy and Enchanting skills became equally familiar with Console commands after losing an orphan somewhere between Windhelm and her cozy little home in Whiterun. It isn't even immersion-breaking; typing a few lines and having a person magically teleport into your presence isn't any odder than the things that happen all the time in a magic-filled world like Tamriel.
But back to the point. I messed with the Creation Kit over a couple of evenings. I managed to turn one of the ubiquitous tree stumps into a specialized Crafting Station that would let you fabricate a stone axe from firewood and a lump of rock.
I had thoughts about making an entire lithotechnology mod. It would be amusing to enough people, I think, to be of benefit to the larger world. There's a mod I've seen by someone who has studied way too much Geology that rationalizes all the materials around a huge list of real-world minerals.
Mostly I'm not doing it because I do enough in life already. I have things I've already promised to people, and I'd hate to add to that list. The other reason not to do it is because it wouldn't integrate well with the world.
Sure, you can play a hunter (people do), who lives off the land. I've seen camping mods, mods that improve hunting and wildlife in general, even fishing mods (that show a similarly intense interest in fishing as the above mentioned did in Geology).
Thing is, the world of Skyrim is relatively small, and it gets a lot smaller as you go up in level. What's the sense of making flint knives and wooden bows with Clovis points on them if the next day you have to defend yourself against a roving bandit and (assuming you win) can loot good Nord steel off his body?
The technical challenges are still intriguing. I got far enough with my experiments in modding to see where some of the difficult elements would be. The nastiest is that importing new models requires a bunch of tools and processes my work in Poser content creation is insufficient preparation for. And new animations? Pretty much a closed book.
There is also the little matter of putting the materials into the game. The tree stump hack I mentioned above was done that way because by modifying the Class object, every single instance of that stump in-world became one of my custom crafting stations. You'd have to do something similar to make flint, obsidian, river stones, etc, appear in-world. Otherwise you'd have to go into the editor, go into a whole bunch of cells, and insert new scenery/objects.
Another difficulty is that I think of flint-knapping as something you can do anywhere. That it doesn't need a dedicated crafting station. This goes against the Skyrim philosophy a bit, as Crafting is partially controlled and game-balanced by making you have to go to one of a limited number of locations. But there's at least one mod out there which breaks that already.
Which is the Campfire mod -- a mod almost certainly going to be installed by anyone who wants to be living off the land and making their own arrowheads. And as a matter of fact... the creator of the Campfire mod has provided his own Creation Kit and has already been surrounded by a small modding community of his own! So there are tools, there, to expand the making of kindling and bedrolls at your temporary campsite, to the making of both lithic tools and the tools (flakers, billets, etc.) to make those tools.
Ah, well. After my recent would-be Bard adventure, I'm equally inclined towards making a mod that would let you craft -- and improve -- your own musical instruments at one of the standard in-world crafting stations. Ah, but it would only make sense if you needed a Luthier skill to make certain instruments, and improvements in that skill would allow higher quality (and more expensive) instruments, and such instruments would give bonuses to Bardic performances.......