I really hope 'hard mode' to people doesn't mean higher levels & more grinding. I get that grinding is just part of JRPGs for some people, but I've never thought of it as fun or challenging; levelling up your pokemon doesn't require skill or strategy, just a willingness to waste time. It was definitely annoying that there wasn't the option to switch off exp share, but I actually enjoyed using it. The combination of exp share with the access to the pc box outside of pokemon centre allowed a more diverse team of about 9/10 pokes that could be rotated.
What I'd like to see is an ai that isn't dumber than the average rock. Granted, I have absolutely no experience of game development & the technical requirements that would be involved, but surely it can't be hard to improve them somewhat; they literally almost never even switch out when they are at an obvious type disadvantage. Maybe the 'good trainers' (e.g. gym leaders) could be programmed to have some sort of knowledge & prediction. If they inherently knew the learnset for all pokemon in the dex/region (which would be plausible in game, given that they are supposed to be pokemon experts) that could allow them to switch out to a favourable match up. Likewise understanding stat distributions, such as which pokemon tend to be on which side of physical/special split etc, might also allow for a degree of prediction. And it almost goes without saying, but either other trainers should have full parties, or you should be limited to matching up the number of pokemon they have (esp with gym battles). All of this would mean winning becomes more about actual understanding of the game & strategy, than brute forcing your way through and to me that would be a lot more satisfying.