Is it possible to unhide only part of a mesh? So I'm working on a mesh with sub-meshes, and as I work on various bits of the project, I hide other parts to make it easier to see what I am doing. 

So I work on one thing and hide a few predefined vertex groups and a random group of vertices, and do more work. 
Now I want to make a change to one of the vertex groups, and I'd like to unhide only that vertex group.

I haven't found a way; has anyone else? Is this worthy of a feature request?
I think you might be interested in the Mask modifier.

This modifier will hide everything except the specified vertex group, or the other way around if you have the invert icon selected. To hide multiple vertex groups, you can add multiple modifiers:



Make sure the modifier is enabled in edit mode (triangle icon).