I really think that a perfect monk build would be to combine spirit and martial arts dice into spirit dice, and your unarmed strikes deal spirit dice damage, starting at d6 (d8 if fully unarmed with no shield), making Unarmored a choice, maybe a level 1 choice that focuses you more on speed and finesse, or strength and ability to move creatures around and stuff, and wisdom and defense/support of some kind.
Then, make about a dozen spirit features to choose from at level 2, 5, 11, 13,16, 18, build flurry into martial arts, step off the wind and slow fall into Unarmored movement, and patient defense and the basic atwill part of deflect [attacks] into Unarmored defense. Spirit Techniques would include immediate stuff and stuff that lasts for longer, and you learn maybe 9 ever, keeping things fairly simple.
Then take most of the later level abilities and make them chosen from a list similar to warlock invocations.
In the mystic, I’ve gone with more of an infusion type deal, where you know more than you are using in a day and can change every day, representing focusing your mind and body on a set form and style even though you know several.
For a more direct monk update I’d probably go more invocation where it’s a set list that is always active.