Basis isn’t a “deduction”. Basis is just what the word means: — the “base” value of an income-producing asset, upon which profit (income) or loss is based.
Put so that perhaps you can understand it: if you cash in a bank CD, you don’t pay flat tax on the whole amount of the CD, because you yourself GAVE most that to the bank on deposit. You pay tax on the INCOME from your “base value” (principle), which you and the bank call “interest”.
Its “principal”. But, your scheme is just as complicated as the present situation. Seems that we need both a sales tax and a lower income tax. Otherwise, folks will go offshore to buy, thus harming the economy here.