My first question is how are you going to sell someone all the materials without the cab? You'll have to answer tons of support messages with people asking you about how big of a cab, what material, guarantees, etc. So if the current sellers aren't selling suitable cabs...how are you offering a better "deal" by selling components with NO cab?
Even if you did offer a cab with components...even then, why are you better than the other sellers? What makes your cab or recommendations better than cabs that are pre-cut (need assembly) and those that come prebuilt? If their cabs aren't "good" why is yours "better"? How is your cab going to be a one-size-fits-all that beats everyone elses offer?
Will you have social proof or testimonials on how well your kit performed?
Good idea, but looks like you got more kinks to work out before taking it to the market.