Wow Tycho, you've done what I always thought about doing with the grid system, but never got around to it
I thought it would be too difficult and there you are having executed the thing and also in an absolutely beautiful way
I would love to add your grid system to my mod, but the whole credit for this belongs to you. This needs to be released as a mod of your own. You can release it as a vanilla version and I'm sure lots of people will find a need for it and it will be quite easy to mod it into different GUI's.
Please, contact Neal Stevens or Sailor Steve to get the right to upload a mod to the downloads section and release this as a mod of your own