Establishing a death ending, locking players out of questlines when they do certain things, all this encourages a CERTAIN playstyle, a certain playthrough, to get the maximum amount of gameplay. To get a certain ending. In the end, all you do is have a bunch of players gaming the system.
FWIW, I don't like death endings, either. It too often feels like a cheap gimmick, especially in a game that doesn't have to end because the one quest line is over.
However, I disagree with not locking the players out of questlines if they do certain things. You don't have to do everything in one play through. That's the beauty of open-world, that you can go somewhere or do something, and stumble into a chain of events that has implications on the world. You can also have another character that doesn't stumble into those events and doesn't trigger those implications, allowing different scenerios to play out. Not having the world recognize what you're doing just makes it feel static and unliving. You should try to avoid thinking there's a "right" playthrough order to quests.. it's a sandbox game, and the way you play will always be "right". That doesn't necessarily mean you can do whatever you want whenever, though.
That said, paths don't need to be closed off for the sake of being closed off. Just because you join the Fighters Guild shouldn't lock you out of the Mages Guild, for example (as long as you meet the skill requirements). But the world should react logically to your choices...if you become a ruthless murderer, anti-murderer groups should respond in kind.
I agree. There should be consequences- but only if there are ways around those consequences
It's not much of a consequence if it can be avoided or worked around, is it?
Do NOT punish players when they have no idea of the consequences.
I would add in "harshly" there, but yes, I agree. Don't harshly punish players for something they couldn't have forseen.