What's more, is who gets to decide what is a necessity. Once upon a time I flew to Australia, bought a commercial van, a surf board, and converted it into a camper and travelled a loop around the country. I was by definition poor and homeless, but I was in heaven. I don't think this would qualify for any tax breaks under your plan. In this way your plan creates a complex tax code that does not align with me maximizing my utility function.
There are vast benefits to simplifying the tax code, and I would argue a better version of your idea is to guarantee a basic income to everyone.
BI won't work for everyone, such as the truly disabled, but it's a more efficient way of reducing inequality for the truly poor, and more capable of maximizing individual utility functions.
I know you will say "but who will produce useful goods and services," but at the moment I would wager far less than 30% of the population produces useful commerce. The labor participation rate is only about 60%, and many jobs don't produce anything useful. For example, police officers in Utah that settle for 0.5MM for unconstitutional injustices are draining taxpayer funds. Wall St is completely out-of-control. Bureaucracy, military-congressional-contractor-complex, healthcare insurance companies... There is an extroardinary amount of waste.
BI would also benefit the economy by increasing aggregate demand. It would stimulate investment by providing a safety net for indivisuals deciding to retrain or invest in education.