I agree with this concept for the most part. I think the only concern is that the black market for these luxury items that I'm assuming you're now taxing in the range of 20% (new phones, new TVs, etc etc) would go through the roof and then the government is earning less money because they aren't getting anything on that now. I do definitely think this is an improvement on the current system though.
I think some combo as
@prlyles said is probably best. As with anything, the best solution is generally a combo of the best parts of a few ideas...but again, that concept is completely lost on 90% of the population these days.