Seriously, go play Oblivion. Experience the horrors of level scaling on exploration.
Why in the world would I do that? Your entire argument against level scaling seems to be entirely based on how badly it was implemented in Oblivion. As with any tool, using it wrong or poorly is going to lead to undesirable results. Exploring badly designed games for some kind of insight into a particular mechanic is pointless when I can turn to numerous well designed games and see level scaling at its best.
The problem is you, for what I hope are obvious reasons, are determined to go on pretending that Oblivion is the only example to look at when judging level scaling. I can list a half dozen examples of games where level scaling worked very well, but you will just continue falling back to Oblivion's bad design.
Okay, here's you anwer;
* Expansion will raise level cap (there's a shocker).
* Mods will add appropriate content for the environment it's added to (if it's good that is). Unless someone intentially wants to make a lvl 20 encounter area in Cyseal. More power to them. They got all the freedom they want designing. I absolutely see no issue there myself. Why would there be issues?
(Not to mention total conversions do indeed generally force you to restart. It doesn't make much sense bringing your full character into a total conversion mod, most of the times. I'm sure there will be 'arena' mods that will allow your character to test it's maxxed out metal)
Maybe if you actually raise concerns I can answer them. Because as far as I see, there are none, just like with the current fixed enemies approach. What's wrong?
You seem to be responding to questions I never actually asked.
Although I've repeated this twice now, let's go for a third time. Since Divinity : OS allows players to progress in different ways, it stands to reason that players might end up with characters at varying levels by the time they reach the end of the game. You might, for example, wind up with level 20 characters, where as I wind up with level 23 characters because I'm a completionist and have participated in every quest the original campaign has to offer. Someone else may have level 26 characters because they kill all NPCs, friend and foe alike.
If we get an expansion, or if players use the editor to create additional modules/adventures, what level should the starting monster in those expanded adventures be? 20? 23? 26? What's the "right" magic number when all our characters can end up at wildly different levels (in a large part due to the freedoms allowed in this game)?
How would *you* make your module for the public? How are you going to balance a starting point for multiple character levels since the game doesn't automatically scale opponents to the character's level? If I release a module where the battles start at level 25 and you only have level 20 characters.. what good is that module to you? If I instead make the battles start at level 20 and someone has level 25 characters, how can I hope to keep them entertained when all the fights will be trivial due to the level difference?
For that reason, I suspect most new adventures will require players to create new characters each time (since having opponents starting at level ~1 is the safest bet), which is too bad for people that want to continue developing their favorite characters. Level scaling would have helped avoid a lot of issues here.