What are the implications of this very short stun ability?

Question

In the process of homebrewing, I came up with this rough outline of an ability:

As an action on your turn, you can speak words of rebuke. Creatures [in the area] must make a Constitution saving throw [against a specified DC]. On a failure, they are stunned until the end of the turn.

The primary purpose of this ability is to act as a concentration breaker - however I want to be aware of any unintended interactions such an ability can have - for example, if abilities such as Rage end on being incapacitated, however briefly, or if doing so causes a flying creature to fall.

I should point out that the 'on your turn' wording is there to prevent abuse including readying this action.

Answer 1

Borrowing from my answer to a similar question there are a few unexpected results of being Incapacitated (which happens when Stunned):

• An incapacitated creature does not cause disadvantage on ranged attacks in close combat.

• An incapacitated creature can automatically be grappled and automatically be shoved.

• An incapacitated creature loses concentration on spells.

Additionally, the Stunned condition also causes the following:

• The creature automatically fails Strength and Dexterity saving throws.
• Attack rolls against the creature have advantage.

Most of these facts are not going to be easy to use for most characters. That said, people could optimize their characters to use this feature by having Action Surge, the haste spell, or bonus action ways of doing these things.

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With a team of party members this can rather quickly be capitalized on. Simply have one character Ready an action for when the Stun succeeds and thus any spell or feature that benefits from a target being Stunned (like disintegrate) can receive the full benefits of the Stun even though it isn't the caster's turn.

The most notable single-character use to me right off the bat is a Sorcerer using Quickened Spell for a guaranteed failure on the save for meteor swarm or disintegrate or even on a regular bonus action spell like grasping vine.

Answer 2

Looking at How can a player character cause the stunned condition? we see that there are "5 spells, the Monk's Stunning Strike, and a few items" that can stun, and they all cost an action plus some resource - monetary up front or ki / spell slot.

As already shown in the question and in answer by Medix2 even with the shorter stun uses are plentiful and powerful. If you will allow this feature earlier than Monks or even at the same time, you will severely step into their niche, possibly upsetting monk players. Monk is supposed to be specialist in such tricks, but he still can only stun one at a time, and for a price.

Similarly with casters, "free" stun when they have to pay a 5~7th level spell slot for it may be discouraging, especially when they used up a spell known limit or gp to write such spell into their spellbook.

As written, this feature would diminish the usefulness of stunning monk and stunning spells, they wouldn't be worth as much as they are now. It will also remove the need to decide if stun is needed now or should be withheld in case next fight would need it more.

The need to coordinate ready actions hardly balances that, but increases the time players will spend talking what to do instead of actually doing it, making fights even longer in terms of real time.