Okay, so this is kind of an odd idea, I guess. But I like to think of my 'main' playthroughs of each major questline as all existing together, Ie that in my headcanon my Dragonborn, Archmage, Listener, et cetera all exist across.. my version of Tamriel; this makes at least a little sense considering that canonically all of the questlines are completed, but they almost definitely weren't all done by the same person.

Anyway, my question is, does anyone know how I would go about making quest progress persistent across savegames? Obviously doing this dynamically would be impossible and/or extremely difficult; that's not what I'm asking how to do. If anything, I would likely set up an ESP with each of the quests 'completed'. I'd need to find a way to make it so that some of the dialog and events trigger but not all of it- for example, I would want dialog acknowledging the events to be triggered, but I wouldn't want the player to be acknowledged as the source of the actions. In some cases (IE The College of Winterhold and the Companions) I'd need to replace certain or move certain NPC's- for the College of Winterhold, I'd need to replace Savos with a lookalike NPC of my archmage character; find a way to make the other NPCs treat my archmage as the Archmage; move Savos, Mirabelle, and Ancano to some cell where they won't escape and whatever, along with obviously more work.

I'll be frank. The idea didn't seem like so much work in my head- now that I've typed it out it seems impossibly complex. But I figure that I might as well ask, if only as a learning experience.

In Oblivion, there is the Wrye Morph mod. It allows you to shift from one character to another mid-playthrough. Not exactly what you are asking for, but I think it is the closest thing that exists. Unfortanately, it is for the wrong game.

It is complex, and part of it is possible(from my understanding with quests), but it'd take a lot of hard work on your end. Not even I would bother going through all that. You'd have to go in all the dialogues and change their conditions to how you want them to trigger, and it doesn't stop there. You'd then have to check quest stages and make any changes needed. Obviously this is not something you could release to the public because the conflicts would be massive(just putting that in there).

Anyway after doing that, in theory, with a new char it would appear that the NPCs would acting as if someone else did the quest, or something. If I understand you correctly.

Can I not make one post where I don't have to edit a typo..

Yeah, that's what I thought. I didn't realize how much work it'd be until I typed it out.