Having more options for your player base is going to be better. I don't think anyone can reasonably argue to take away options (e.g. remove difficulties, remove spells, remove classes) and so I would think the inverse would be true. There seems to be quite a lot of people who would be interested in some sort of higher difficulty without having to use a bunch of mods. The mods are still available to go beyond that point of course.
That being said...........
I think the biggest issue in a higher difficulty is not "would it make the game better" but rather does it make sense for Larian to do so from a time perspective. Some of the suggestions have frankly been rather greedy and not at all realistic, and while personally I love the creativity - I just don't see it being feasible.
I think Stabbey had a good point in another thread about everything with the definitive edition being wrapped up by now so nothing we suggest is going to make it into that outside of a patch. Assuming this is the case - any difficulty suggestion would likely need to be something on the scale of what goes into a patch.
I'll advocate for a higher difficulty for the rest of my days but I also understand we need to be realistic. And, while there are a lot of us interested in a fancy higher difficulty we might want to keep our suggestions very simple if there is any chance in them being adopted.
To that end...........
My suggestion still remains a significant decrease in (EXP, GOLD) for players and a significant increase in (ARMOR, HEALTH) for enemies. I could be wrong but I imagine something like this could be done very simply and could be achieved with a check box on tactician rather than a whole new difficulty name.
I realize to some this just doesn't seem like a priority to them, and they enjoy the current difficulty options - but many of us who are looking for more of a challenge feel it could make a big difference. If the shoe was on the other foot, and I was in a thread advocating the addition of some element that was meaningless to me, but seemed to have a strong following - I would at least be neutral if not supportive of their efforts. After all I think we all want the game to be as good as it can be, allowing people of all different types of gaming preferences to enjoy themselves.
After completing countless campaigns over absolutely ridiculous amounts of hours - my group of friends feel that having the greater challenge would increase our enjoyment considerably.
@Larian - I know everyone asks this but it would be great if you gave us some of your thoughts on this concept. If it isn't something you guys are interested in doing I'll stop posting about it

. Thanks regardless!