The 'Lighter' Side Of The Force
The theory makes sense. Like you mentioned though, there is the question of how Qui Gon's lightsaber made it to Obi Wan's hut on Tatooine. It's unlikely he had much time if any to grab anything from Coruscant before heading to Mustafar to confront Anakin.
I like this theory a lot. I do wonder if it could be a synthetic crystal or a black market crystal. Didn't many Jedi lightsabers become collector items for the elite rich?
I Heard another theory about Luke's Crystal, That When Empire Took Over, they started to destroy every single known jedi temple on Ilum and Kaber Crystals that were in there, But when Luke Created his Second light saber, Somehow he created The Created The Crystal Itself! And of coarse got the Lightsaber parts from old Obi-wans hut.