make a person's entire income subject to the Social Security tax, and institute one uniform rate for everyone to pay.

The Social Security tax is regressive for two reasons:
1) There is a cap on the income that is subject to the tax, so the wealthier a person is, the lower the percentage of income for which that person pays.
2) Self-imployed individuals are penalized because they do not receive benefits from their employers, often do not have the security of steady employment, and they must pay a higher rate for the Social Security tax.
In the spirit of fairness, a person's entire income should be subject to the Social Security tax, and there should be one uniform rate to be paid by everyone, regardless of whether they are self-employed.
This structural change would also help to ensure the financial viability of Social Security.