This is the second place I am posting this but I think this shouldn't be ignored in the discussion I am in the group that I am happy for small changes to the game. But I think something people are missing from both sides is a lot of the QOL stuff they ask for you can already do with mods and that is whether they keep the api the same or update it to current wow api. You will end up with a lot of this stuff in general.
Here is a few screen shots what is possible right now with mods in a vanilla client I will not mention where this came from.But this should work to show mod capability off. I highly doubt they will ever let the model thing fly but I wanted to see what all I could do it took me about 2 hours find all this stuff and set it up.
https://imgur.com/a/G6ulA
Now aside from the model mod because there is no way blizz will let that kind of thing fly.That was there more to just to show things off if they had the current models. A lot of the functions I have seen people talking about can already be done in the old vanilla modding api and in legion api but things like auto looting a quest helper. Or even a premade dungeon finder that I found that works almost exactly like the current premade group finder.That stuff isn't needed in current wow so no one is going to make a mod to do that.But in classic there will be you can already see people on these forums that want this stuff added to the game.
All of that can be done in there and that is based off the old vanilla api. While it is highly unlikely blizz will implement much of this.A lot of it will end up as part of the game anyways. This is what was done with very little mod support. But just with classic existing it will change the modding scene. Some people will play with not a single mod but they will exist they will be affecting the game in very different ways from the original and it doesn't matter what version of the game they release because mods not existing seems incredible unlikely. The api is not as different from vanilla wow to live as you would think mods have been back ported and they are even more certain to be back ported in classic and for new ones to pop up.