Making my own Modifier : Make Texture operate as mask on vertices I’m would like to perform on operation in blender that I don’t think I can yet, I would like some help on how I can develop it in the right way.

I would like to delete geometries depending on a texture and following the UV map.
Imagine the Displace Modifier, where you indicate the texture and that you want to use the UV but instead of extruding vertices based on the grey level, it would delete or keep vertices based on a threshold.

Because you can’t create modifier as addon, I’m already making my own from blender source code. I believe it is actually ready, what do I need to do so that my modifier appears with the other ( precisely ) ?

Also after that I will aim do the same thing but with subdivide operation, where my mesh will be subdivided more in specific area depending on a grey level texture.

Any help is welcome.
A possibility (to avoid a bit difficult coding), more than a real answer: 

Use a displacement modifier on a cutting object.

Then use this cutting object for a boolean 'difference' operation on the object you want to cut (or remove some vertices).

This is illustrated in this animation: