In the new UA, aside from the unnecessary "once per turn" restriction and shortened duration, Stunning Strike got another modification (most likely an oversight, since WotC apparently does not proofread): Stunning Strike can be triggered by an Unarmed Strike or an attack with a Simple Weapon. Notice it does not say "Simple melee Weapon" nor "a melee attack with a Simple Weapon", this means that any simple ranged weapon (mainly the shortbow) and trown weapons can trigger your single stun attempt for that turn, which seems the safest way to play Open Hand monks now that the reaction sealing is an even weaker Stunning Strike; Shadow and Elements can do without it, in fact they are better off without ever bother to even try it.

The lack of any additional ASI (a really simple, but not complete, fix) still means that the Dex, Wis and Con are going to compete over priority, but since the new capstone is just as worthless as the old one a single Warlock level could be used to create a Wis-based Handaxe (or the Yklwa if allowed) and increase your Ki save at the same time.

Admittedly, WotC foresaw monk players using Pact of the Blade this way, so that may be the reason why no weapon can be used with the MA die (apparently, a d12 shortbow/handaxe is way too powerful and completely breaks the game). That being said, this combination is roughly doing the same thing Astral Self has done before (albeit without needing Ki for the Arms), but Astral Self would be better now because of the increased MA die and the lack of monk weapons.

Maybe adding an ASI at levels 6 and 10 would help. Also, I had totally missed the lack of limits on stunning strike regarding melee v. ranged. Good catch.

Maybe 2 might be a little too greedy, but 1 seems enough. There are some monk features that are build-defining, so point allocation is important and having at least 1 more ASI would make distribution a lot easier. The most build-defining features IMO are these (in order of relevance):

1. Subclass
2. Unarmored Defense or Constitution modifier (it usually is one or the other)
3. Stunning Strike

With the new UA Stunning Strike is not that relevant for the build anymore (except for Open Hand) and the emphasis should be put in the new subclasses:

• Shadow can completely focus on Dex and Con thanks to the improvements to Shadow Arts (many complain about losing Pass Without Trace and Silence, but the new Darkness more than makes up for it), since being able to almost always be in Magical Darkness means that you can somewhat ignore your Unarmored Defense;
• Elements can focus on any of the 3 scores (Wis is only really needed for the push/pull and the elemental burst) since your attacks will almost always be at range Unarmored Defense is not so important, so you can go in any combination Dex+Con/Dex+Wis/Wis+Con;
• The real problem comes from Open Hand, high Wis is a priority, there's no way around it, but because the new Open Hand technique is still restricted to FoB (meaning you will always be restricted to only 2 attempts to use it per turn) you really want those 2 unarmed strikes to land so high Dex is also mandatory, Unarmored Defense is important here because Open Hand restricts you to melee and if either you miss the hits or the enemy makes the save, you will need a high AC to avoid the hit, this means you must focus exclusively on Wis+Dex, points for Con are only allowed if you rolled stats. Sadly, Stunning Strike is now more powerful and (arguably) just as restricted as the Open Hand technique, so the only solution is to multiclass and get a ranged/thrown simple weapon to use your single stun attempt per turn from a distance. Problem is, this is only possible from lvl 6 onwards, because Stunning Strike+Pact of the Blade need a lvl 6 character, so an Open Hand monk will really hurt on the previous lvls.