Well IMHO mad is not quite the right word, but then again: it’s not my native language.
I think it has more to to with an attitude of: who says it can’t be done? And then doing it!
Congratulations: CRX for being able to build such a light, and Agro for owning that light.
I think CRX didn’t like the purple colour either because the light is natural Ti now. And I’m glad about that. 
I did some calculations as well as experimentation on that.
How strong must a switch be to act as the only spring?
For AA cell, gravitational force is 0.215N. The switch needs a some more to overcome friction. It also needs some more to not be pressed by shaking the light, this is probably more important than friction.
I tried with a 0.8N switch and no tube. As expected, the switch can push the cell against gravity easily. But with that weight it becomes very sensitive, the force needed to press it is surprisingly low. Seems too low.
I would be really interested in double-action switches in such use. A quick search shows that there are such switches with the first action of 1N. Might be OK for AAA but I doubt it’s enough for AA. Anyway, I intend to check.
Single action switches are available with forces up to 7N. This ought to be easily enough.
How is the cell positive connected?
A piece of copper foil.