Basic Income has lots of things going for it, but it doesn't feel like the exactly right answer. I'm more in favor of a linear income tax (with no writeoffs or exemptions) where the intercept is set to equal what the basic income would otherwise have been. And this tax should include *ALL* sources of income and replace all other taxes.
Think, don't just "feel". For your information, write-offs exist because investments actually do reduce your income. If you don't allow them, someone who spends $100 to gain $1100 (net income: $1000) might be taxed $440, and someone who spends $2000 to gain $2500 (net income: $500) would be taxed $1000. Does. Not. Make. Sense.