Media Library & alphabetical Uploads subdirectories

For the past several years my site has had the Uploads folder arranged like this:

uploads
—diary
—downloads
—images
——a
——b
etc

The images are sometimes reused and are therefore stored so that I can find them. They are named carefully and then stored in alphabetical sub-directories. “springsteen-manchester-2011.jpg” would be found in uploads > images > s for example.

I have been managing this manually using ftp to upload the images and self-written shortcodes to insert them into posts like this:

[imagery folder=”m” file=”mcluhan-tetrad.jpg” label=”An example layout for a tetrad”]

I am now looking at the benefits of switching this to use the core Media Library, but I cannot find any documentation about how to make the Media Library use a different path than the default uploads > 2012 > 09 path.

What I want is for the Media Library to look for images in all the sub-directories in uploads > images – which consist of 26 directories labelled a to z.

Crucially, I also need the Media Library to store new images into this structure correctly. If I upload “campbells-soup.jpg” then it should be saved into uploads > images > c and not into any date-related folders.

Is there a way of doing this (without changing the core files)?

Cheers
Owen