Need a bespoke photoshop/illustrator script (other solutions considered!)

I need to create a fast, accurate workflow for creating Paint by Numbers from any image. So basically; The image must be simplified to only contain 24 different colors, The boundary of each color must be separated by an outline. Then each color needs to be replaced by a text number. I have a color pallet of the available colors i use if this can also be incorperated into the workflow. I essentially need to be able to upload an image, and in the most efficient way possible.. create a paint by numbers kit where i can assign each number to a color in my pallet. Can ANY part of this workflow be replaced by an action/script? Possibly using illustrator, photoshop, a combination of these.. or anything! If you can find a way solution to speed up this workflow - i'm interested ;)! I've attached an example below!