Can it use Gmail's classification of e-mails as "important", "not important", "updates", or "promotional"?
Then your label will appear in your desktop client. Kind of a hack but I did this for thunderbird and it works.
As for making a plugin that handles this automatically - I'm not sure it's even possible, but I'd love to be proven wrong!
On second thought, the initial setup doesn't really need a plugin so much as the way categories are displayed. Especially cool would be to have them as tabs like in the web interface: once you get used to them, you find them sorely missing in desktop clients. I always find it weird to have my personal, social, and "promotions" emails brutally mixed together.
Unfortunately Gmail doesn't expose updates/forms/promotional via IMAP, so we can't show those. But they probably wouldn't be that hard to add in a plugin... ;)