If someone wants to bypass something by grinding, thats their problem imo. The issue is that these challenges only solution is grinding or massive rng luck with low rolls.The main issue is that "adding difficulty" in a Pokemon games can realistically always be bruteforced by grinding.
The only way to add some ""non-grindable"" difficulty would be using gimmicks (like they've done for Totems or Ultra Necrozma), but even then, it still can be bruteforced if you really want to.
Unless Pokemon games introduce a true dynamic level scaling (aka, "boss" battles scale with your average level, making so that you can't overlevel them), they'll never be really "difficult" without just having the option to grind it out.
It's sadly a curse of Turn Based RPGs, unless there is a way to stop the player from overleveling, you always run in the problem of "grind to win".
Grinding as one of the options is fine, some people are into that for some ungodly reason, but the point is more making fights that allow you to win if you do things like switch around teammates (would be a good use of the box mechanic in gen 8), use some strategy, etc. Like idk if a gym leader was a hyper offense team but had weaknesses like bad defense and crippled by status, and theres a very good prankster dude you can find if you search for it on a route, or a stally gym leader that hates pokemon who can just punch them very hard. Have the trainer face different battle strategies and adapt to fight them yknow?
thats a good option for ppl who want, but I dont want to prevent people who like grinding to not be able to do it in a vanilla game. have it be some kind of "mod" that you get when you beat the game, maybe add some other challenge mods like nuzlocke-esque stuff (rename it so it remains child friendly tho lol)Technically they can use anti-grinding mechanics that don't only apply to traded Pokémon. In one ROM Hack I once played (Pokémon Pyrite), instead of the "badge obedience" system, Pokémon outright couldn't earn any experience at all after a certain level, until the next boss trainer was defeated.