Having never handled the kelly kettle, I have similar questions. And I don't think it's going to be fully useful FOR ME.
Because it can only boil water, it's only useful as a second stove. And for a second stove, it's too volumous and heavy. If it's the only stove, I don't think a pot is going to balance well with such a narrow base and no support. I'd also have problems finding a nesting pot for it to descrease packed volume.
If I have a choice between packing a kelly kettle or extra fuel for my first stove, I think I'll end up going with extra fuel. No soot. No hassle and faster boiling times.
I had the similar problems with jetboil. I rarely ended up taking it as the only stove.
Methinks as the ultralight woodchip solution a hobo stove with a nesting titanium cup would be lighter and more flexible. It can be the only stove, because it's short enough to cook on. It should also be smaller and lighter.
YMMV