Some thoughts.
From what Bethesda and Valve have said following the paid mods fiasco, Valve were a significant driving force in that attempt, in large part because it had worked well for other games. Bethesda have said that FO4 mods won't be paid, and I think they had their fingers burned badly enough that they're going to stick to that. So "possibly paid" is, I think, more in the realm of paranoid fear than significant possibility.
Hi-Res packs may not be entirely out. I've no idea what the graphics capabilities of the consoles are, but I'd be surprised if there weren't some areas of the game that could safely have higher textures applied. But certainly extreme, across the board hi-res packs seem less likely for consoles.
Mods that require third-party tools could easily be supported on Bethesda.net. It just means that when modders upload mods they'd have to say what, if any, third-party tools are needed, and those mods that need them wouldn't be made visible to players browsing for mods on a console.
Mods suitable for console could be very wide-ranging. There's a lot that can be achieved with Creation Kit, new models, new textures and scripting, far beyond 'vanilla'. And we really don't know what new features will have been added into Papyrus for FO4, but there may be somewhat less need for a script extender - that's a question only time will tell. However, a potentially big problem will be the voiced protagonist. Previously, if a new NPC had a slightly poorly acted or recorded voice (or even silent voice needing subtitles), well, that's mods for you. But trying to get sensible speech fragments for the protagonist could be hard, and having them silent with subtitles could be very jarring. So that'll be limiting.
My big concern is for model editing and creation. Bethesda haven't released model exporters since Morrowind, I believe because the exporters they use in-house have so much licensed middleware incorporated, and there's no way they can re-license it. From Oblivion to FO3 to Skyrim, getting models from a 3D modelling package into the game has gradually got harder. The teams that have, with great effort and ingenuity, produced exporters, have few members. The skills and effort needed are just too high to attract many coders to that unrewarding hobby. As a result, I don't believe there's much in the way of straightforward or up-to-date tools out there, and with FO4 there's a real risk there won't really be any.
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On what sort of mod content will be allowed, the impression I got from interviews with Bethesda is that pretty much anything that doesn't have stolen copyrighted material, depicted six or nudity will be allowed. They've certainly said explicitly that they're not against mods that could break player's games - largely I suspect because there's no way on earth they could ever test mods thoroughly enough to prove they were entirely bug free, so have decided not to worry about that at all and just be up-front about the risks players take downloading mods.
As for curating... well, the fact is it's impossible to say. They could do some very basic curating as an automated process (no new character/creature/clothing models or textures = no nudity, no new animations = no explicit six), and those could be passed through without a second glance. Delaying mods on console, and when they do become due for release, checking comments and complaints on the PC release, would allow them to quickly spot inappropriate content without actually looking at the mod themselves.
But there may simply be more work than either Bethesda, Microsoft or Sony can deal with by way of curating, and they might simply have to rely on a complaint/report system.