A full rewrite of the tax code might cause a bit of temporary screwiness with the economy. That's because whole businesses have their business models built around tax minimization, especially when it comes to depreciation rules.
Any accountant will tell you running your business for tax reasons is the best way to go broke.
Getting rid of depreciation rules should be the FIRST order of business.
Depreciation only makes sense in an INCOME TAX world. In a spending tax world (sales tax or vat), it becomes meaningless.