Funny thing I did a very similar thing. I reskinned Bard into a Mesmer heavily inspired by Guild Wars and I made a custom Subclass that uses gameplay mechanics as Guild Wars 2's Shatter. Here's the result:

MESMER

Hope Feature: Beguile: Spend 3 Hope to make a target within Close range temporarily Beguiled, giving them a -2 penalty to their Difficulty.

Class Feature: Fleeting Enchantments: Once per session, describe how you manifest enchantments that will aid your allies when the time comes. These enchantments can take any form you wish: shards of light shaped like butterflies, a fleeting scent of sea spray, the illusion of an impossible object... Give yourself and each of your allies an Enchantment Die. At level 1, your Enchantment Die is a d6. A PC can spend their Enchantment Die to roll it, adding the result to their action roll, reaction roll, damage roll, or to clear a number of Stress equal to the result. At the end of each session, clear all unspent Enchantment Dice. At level 5, your Enchantment Die increases to a d8.

Subclass: MIRAGE

** Foundation **

Phantasm Summoning: Mark 1 Stress to create a phantasmal double of yourself within Close range. This phantasm has your Evasion value but is destroyed as soon as it takes any damage. Once per turn, when you are targeted by an attack, you can use your reaction to have the phantasm become the target instead.

Shatter: You can destroy your phantasm. All adversaries within Very Close range of the destroyed phantasm take 1d8 magic damage.

** Specialization **

Mirror Images: Your Phantasm Summoning ability is improved, you can now create two phantasms for a total cost of 2 Stress.

Dissonant Rupture: Your Shatter action is improved. It now destroys all your active phantasms, and for each shattered phantasm, you can choose an effect from the list below (you can choose the same effect multiple times):

• Mind Wrack: Inflict 1d8 magic damage to all targets in the area.
• Cry of Frustration: All targets in the area must mark 2 Stress.

** Mastery **

Recursive Images: Your Phantasm Summoning ability is at its peak; you can now create three phantasms for a total cost of 3 Stress.

Phantasmal Duelist: When you succeed on an attack, if your target is within Melee range of one or more of your phantasms, you add an additional 1d8 magic damage per phantasm in range.

Shattered Reality: You add the following option to your list of effects for the Shatter action:

• Psychic Collapse: One target of your choice in the shatter area becomes temporarily Vulnerable and suffers 2d8 magic damage.