I'm quite surprised that this is really going through the way it is, it's uncharacteristically ambitious and generous from Microsoft and quite tenacious of Bethesda. If the mods are acquirable without money, the way a PC user can then much kudos. Microsoft traditionally charges exorbitant fees to even patch a game; we can look to Valve abandoning TF2 on 360 because it would cost them too much money to patch alongside PC and provide new content that wasn't paid DLC. Also there was the issue with Phil Fish having to come up with something like $10,000+ just to patch the live arcade version of some game breaking bugs. This is a major shift from that kind of mindset.
I definitely understand why it's in beta, and it may be in beta for some time due to the intricacies involved here:
Some mods rely on other mods in order to function, and I'm assuming that submitting modders may have signed a EULA allowing their mod to be automatically installed if a different mod depended on it or something to that effect to avoid issues.
My understanding is that the X1 version has some trouble meeting the 30 fps target, particularly in the Far Harbor DLC. Mods that expand existing areas, add additional NPCs, increase the alpha effects of laser weapons or any number of hardware-intensive purposes would make this even worse, maybe even unplayable. I wonder if Bethesda has a big optimization patch at the ready, or will offer a "switch to 720p" option to allow the usage of such mods, because the X1 as it is now doesn't let the user sacrifice graphical settings in order to enjoy such mods the way PC users can.
Then there's the issue of Fallout 4 not being "finished". Some of the best modding that's been done on Morrowind all the way through Skyrim was after the final patch was released by Bethesda and all of the DLC had been released, and most mods for those games require that one has the latest version and all or some of the DLCs. There's still more DLC coming, and of course more patches to accompany them; the problem being that even a single patch can completely break a mod or corrupt a save using certain mods on the old patch.
My question after all of this: What is the incentive? For Bethesda, for the modders, and for Microsoft? I imagine that X1 modders are going to have (possibly strict) standards upon them, where they need to update their mod in advance of a patch or such situations. They also have to work within the X1's limitations which is extra work, on PC modders can attempt any insane change and basically say "it might be pretty demanding, make sure you have a beefy rig for this one" which isn't an option here. In the back of my mind, I'm thinking money has to be involved, especially after the attempt to monetize Skyrim mods on Steam. Maybe a monthly fee to have access to all the mods, otherwise you've just got amateur and potentially buggier "horse armor" not even made by Bethesda, on top of a $50 season pass for a $60 game. And why would Microsoft offer their servers and bandwidth for free to allow the free downloading of content? So that they can say they're the only console game in town offering this? Regardless, I'm eager to see this play out because it's a game changer, and can have ramifications for modding as a whole and could be a sign of what to expect from Bethesda's mysterious "the next game totally isn't Elder Scrolls VI but a bunch of different stuff" plan. All that said, however it turns out and whatever the motivations are, congrats to X1 owners here. They may have the weaker hardware and lower install base, but they're getting to experience one of the great benefits of owning a more open gaming machine regardless. Hopefully they don't have to pay even more than $110 to have it, and that it improves the experience of an already enjoyable game. And please, if it's one of the mods available, the one that changes your dialog options into the actual fucking sentences that your character is going to say is essential.