I wonder, actually, about the mod-negate-enforcement. It seems to be hard-coded outside the patch folder environment, if what I'm reading on Nexus is correct.
However, I'm not sure it's actually intended to dis-enforce (oh, gods... someone come up with the correct negative, here, my brain is fuzzy. It's midnight) mods for mod's sake, but simply because of the DLC environment. Does anyone remember the weird patch folder issues that came with the Sebastian DLC if it wasn't installed in the correct order with Legacy in DA2? (I had it; I installed Sebastian very late--well after Legacy was released). You had to fudge around the patch folders, remove bits before meeting Leliana in his Act 2 quest and whatnot (it's on the wiki if anyone wants more info). Or his quests just broke. And in that, mods weren't using the patch folder to work, unlike for DA:I.
So I think, yes, they've deliberately kiboshed mods. Hard coded it. But I also think it's to make sure this (and future) DLCs act as intended rather than to be arseholes for the sake of it.
That might just be my stubborn optimism again, though. And I don't hold out hope of them reversing it for a very long time, if ever. Which is just silly (as I've iterated well up the thread, multiple times).