I went through that at my first karate club, but trying to make up your own bunkai, or use someone's else's bunkai, appears to have have no practical value. I own Bunkai-Jutsu by Iain Abernethy, but--apart from the fact that I don't train in Wado-Ryu--I don't see how the text can help a novice or advanced student. A novice student needs to learn from a sensei, who holds all the understanding and can pass it on to the student. That sensei should be using kata to help teach that understanding, by explaining the principles behind each move and how they are applied. The novice student just can't make up those principles for the kata, because they simply don't have the understanding to do so (I've tried!). An advanced student has already gained the understanding of their art, they know all the principles, and can apply them fully. Once again, their sensei should have used kata to teach them, but let's assume that the sensei has not. If so, then what incentive is there for the advanced student to learn to apply the kata? Cross has already pointed out the first one that comes to mind, but that reason has no practical value at all. The advanced student has already been taught the skills and understanding by their sensei, what more will they gain from analysing kata?