Monk is probably my favourite class and in a prefect world I would actually like to remove it completely.
I don't think monk should be a class.
The main problem with monk is that it is a whole bunch of very different things squeezed into the same container. It's pretty wild that the difference between a fighter and barbarian is so minor (one can rage), where as 'monk' is supposed to incorporate pretty much every concept that has a eastern style martial arts flavour, from Dragonball Z to Jackie Chan to the high wire work of HK wushu action movies.
I think barehand martial arts and unarmored defense should be incorporated into the game in general so that anyone could do it, and then you have a host of monk-like subclasses.
Fighter subclass - open hand type monk specialising in battlefield control
Sorcerer subclass - dragonball z blaster type monk
Rogue subclass - ninja et al
Paladin or cleric subclass - mystic/zen crouching tiger hidden dragon monk type
Ranger, druid or barbarian subclass - animal style kung fu type monk
Wizard - this would be your 5 elements type monk
I can't think of anything for Bard, Warlock or Artificer off the top of my head but I'm sure there could be fun options.
This would likely freak people out too much but I think this is how it should be done.