and following an essentially static MQ is fun? in oblivion, no matter what you did, you always get the same pre-determined results which gets boring quickly. really quickly.
besides, with what i came up with, there doesn't even need to be that much change to the MQ. it's like basically a choice for the player if he wants to fight the final boss the hard way or to take the easy route.
personally, it is the main story being static that kills the replay value. if someone wants to experience all the different sidequests and various faction quest chains, just make a save after finishing MQ.
however, if the MQ itself is pliable, the player would be more motivated to clock more hours in order to get their money's worth. How is a role playing game fun if you don't even get to decide what you want to do on YOUR big adventure?
Okay, I don't want Skyrim turning into DA when it comes to the MQ, that would be a terrible idea (In my opinion.)
What I'm saying is that the final ending where you get to stop Alduin should always be the same, we are talking about Lore here.
Sure, I don't mind some subtle changes/variables in the MQ, but not too much where it comes to a point where there seems to be multiple MQs, which doesn't make sense in my book.
Oh, and since when is the MQ a replayable factor? It never was before, why should it be now? You have guilds for that reason, and I even stated that I'd love to see drastic changes that you can make when doing the Factions quest line. You can also make new characters, follow new play styles, RP, etc. Bethesda shouldn't take the time to put in a bunch of variables into the MQ for your replay factor, when there already is a bunch of stuff to do that can cause you to replay the game a lot.
What I'm saying is this;
MQ - Minor changes/variables
Factions - Major changes/variables