Yeah I made some invert for Aharpers Maniquin pees Belgian dubble I think it was.I'll be very curious to hear how your ginger beer turns out. I'm a big fan of Bundaberg, and wouldn't mind trying to clone that some time.
Lots of interesting sugars to play around with. I added a pound of muscovado late boil to a Dubbel I recently brewed, waiting for that to bottle-condition. Never brewed with brown sugar, but used it for bottle-carbing once. Honestly, I couldn't tell the difference, so I went back to corn sugar for that. Brown sugar is just refined white sugar with some molasses added back, after all.
I ordered my jaggery from Amazon, but if you have an Indian grocery, they often stock it.
Have you tried making invert sugar? It's easy and you can control how light or dark you want it. I've made a few inverts (one amber, the other a deep ruby color) that I added to brews. It adds a little dimension.
If you have Randy Mosher's Radical Brewing, he covers the various sugars fairly well.
Yeah I'm sure bunderburg ginger would have to use unrefined cane sugar as their based in Bundy also set up next to the Rum Distillery.