Your entire argument against level scaling seems to be entirely based on how badly it was implemented in Oblivion.
You must have overlooked me taking a few other examples in posts, like Knights of the Old Republic or Dragon Age?
And your entire argument was revolved around how Diablo III, a hack & slasher pur sang did it. But considering you now claim you can give 6+ examples of games with good levelscaling, let me have it!
I just point to Oblivion to show just how level scaling on exploration can have extreme negative consequences to a game.
Kind of important since your whole argument was about levelscaling to make exploration anywhere possible. Maybe if you simply stated "Level scaling will make games challenging throughout" I would have offered to keep looking at KOTOR2 instead... one of the easiest games in existance (and still one of the most awesome RPG's ever! Which would shock you too I guess)
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.
No, they don't... that's what level caps are for.
Despite what some people may think and say that they are 'outdated' and should be banished, they do infact are included for a reason, and the reason is, well, this. There's no 'We have to guess the level of the player on continue' if the level is just simply known. And if the player isn't max level they can simply get there by doing more content they missed out on, which you know there is since we know with finite XP just how far you can get.
So it's not me answering questions you didn't ask, you're asking questions which wont even be part of the equation when the game is done.
Also, I find it very humerous the answer to "That map is lvl 25, I am 20" is according to you "better restart from lvl 1"...

Modmakers will make the levels whatever level they want. You want to add to Cyseal. Check. Want to add stuff for people there right now, or make returning better. Makes the set level different.
Sure, modmakers could put their stuff at the end, but seeing usual RPG gameplay and mods I suspect;
* They will be additions for the maingame (weapons etc)
* Modifications of the maingame (hate repair, change it!)
* Additions to the maingame, usually around the middle.
* Total conversion. Which by design require you to make a new character anyway since a lot of the time everything has changed.
Not everything needs to be added once you finish the game, and only there.
So; still; sollutions to non-existant issues.