A modder named Drayano has pretty much defined this category of ROM hack and I think has his own version of every major game from generations 3-6

There's one called simply Pokemon Blue - 151.

I swear every time I start looking into a romhack that claims to just be a mostly vanilla QoL update they always add in a bunch of random stuff to "fix" the difficulty.

Like, yes I am aware the games are incredibly easy. They're for children. I originally played most of them as children. Just let me get high and stomp all through FRLG with a perfect-IV Feraligatr and the Gen 4 physical-special split. If I wanted to do Nuzzlockes I would.... Do Nuzzlockes. If I wanted a game with difficult gym leaders and level caps, I would go play one of the thousands of romhacks that have that.