I have no specific feedback, but I'm curious how this is being managed. Are you fermenting the kombucha with the Scoby first, then racking to barrels with Brett? Or do the barrels have both the kombucha Scoby and the brett? I think the barrels will end up growing a Scoby, even if you rack off of the initial Scoby in primary. I'm not sure if the Brett will become inhibited by the Scoby, or maybe it will become part of it. Sounds like a cool experiment.
Also, what does the end product taste like? I would assume it ends up being dry and vinegary? I've brewed kombucha in the past, but I'm not a huge fan of vinegar, so I left it sweet and drank it fresh.