Lightroom :: Save Multiple Crop Settings For Single Image?

Let me start by describing my needs. I need to generate proofs for my shoots. I'd like to export images with different aspect ratios for target devices, ie iPad, Android phone, 16:9 TV, etc. What would be really great is if I can select a named "crop setting" in the export window and generate JPGs based on the chosen setting. I've searched all over the place, all seem to talk about presets, virtual copies, etc, which really doesn't address what I want.
 
Fundamentally I'd like to be able to save a handful of crop settings (unique crops but with common names) for each image. I will create the crops manually as I have to pick the position and size for each carefully. For example, on a 4000x6000 image I have these crop settings (for a fairly small area of the image):
 
1. iPad [settings: top-left coordinate (500,500), ratio 4:3, width2000]
2. Android [settings: top-left coordinate (500,400), ratio 8:5, width 2400]
3. HDTV [settings: top-left coordinate(500,450), ratio 16:9, width 2200]
 
As you can see each crop is different becasue I want to be precise about how the cropped outputs look. Then at export time, I want to be able to multi-select a bunch of images and pick say "iPad" crop setting to create the JPGs in a batch.
 
Is there a custom plugin outside of Lightroom that can handle this?