Well, for starters there isn't a universal format to the DA savegames - Microsoft and Sony encode all savegames used on their systems, and they only really allow companies to use these encoding methods to *create* savegames - not to *decrypt* them. There are 3rd party resources which allow you to crack into an xbox/playstation savegame but those are not officially recognized, or sanctioned by Microsoft/Sony.
Basically, there is no way Bioware would be able to take a savegame from a console, and *decrypt* it without Microsoft or Sony's permission to do so, and they are *very* tight when it comes to stuff like that as far as I understand it.
That makes no sense at all. They already decrypt the save when it is loaded by the game that made it. If you can only save but can't load that defeats the whole purpose of saves.
Also, previous DA games (as well as earlier Bioware games like NWN and KOTOR) run on a form of the Odyssey engine. I'm not by any stretch of the imagination a programmer, but I can tell you it's a lot more of a difference going from that to the Frostbite 3; than just graphics. If you've ever attempted to mod a game running on Odyssey, you'd notice that a lot of the things we've been seeing in Inquisition are just not possible to recreate. Stuff like jumping, or fluid combat, or dynamic environments, or the level of customization we've seen in character creation and crafting.
As I mentioned already plot choices have very little and most likely no relation to the used game engine at all. It had to be added to the engine by bioware anyway. Plot choices are just flags, and they would just have to read those flags, nothing else. Everything else could be jibberish as it's not neccessary for this. It has nothing to do with what you're allowed to do in the game world and how extensive customization is. You'd just have to comb save files for plot choices, and ignore everything else.
I also remember seeing a video where one of the devs was talking about being presented with the Frostbite 3 engine and being told that it could not handle four legged creatures. Sure, Bioware proved them wrong, but that really wouldn't have been a graphical limitation. That sound more like DICE believed something in the way the engine handled models and animation would not support a four legged animal.
As fascinating as that is, again completely irrevelant. The engine may not handl four legged creatures out of the box, but that's what I meant when I mentioned no game engine is key ready, there is always tweaking and extending to be done. In programming there is no such thing as impossible. It's just a question of commitment.
Aaand, not to mention if it was just an issue of Frostbite 3 being different graphically from the Odyssey engine, but both had similar hardware and used the same types of files; then honestly I would just pull out the the trusty .gff editor (mod tool released for NWN) I downloaded back during my Kotor days (and still works on DA:O and I'm guessing DA2), and I'd be prepared to mod DAI on launch. As it stands, modding is not yet known to be possible on Frostbite 3. I'm imagining because either the engine does not use the same sort of files as Odyssey did; or because they are *heavily* encrypted and no one has been able to crack them yet. Then again, as I said, I'm not a programmer. I'm only a film student who fools around with mods in Bioware games occasionally. This is what I gather from what we've hard so far, about Frostbite 3, however. 
Again, pulling out plot choices from a save game has nothing in common with modding graphical elements of a game. Different engine uses different storage formats for its content, that's perfectly natural. But again it doesn't make modding impossible, you just need a different tool for it. It's the same with saves, you need a different tool for DA2, than for DA:O, but it's hardly anything near impossible to do.
As I understand some flags are already messed up during the games themselves, that can't be helped, but that bears no significance on the complexity and possibility of extracting choices. What is already wrong would be carried over as wrong, but at least people would have most of their plot choices right, and they could still edit the ones missed with the keep.