You still need your carboys as there's no way to seal the unit off and attached an airlock. Even if you could, why would you want your grainfather out of commission through fermentation!?
They do make a matching fermentor out of the same 304 Stainless. Looks like a stripped Grainfather or T500 Still Spirits boiler - which of course is what it is. I have it and it does double duty as my HLT...with an added Allied Premier 1000W heatstick. If I could've gotten their HLT, I would've but it's not available in Canada as of yet.