Income tax is always an issue, and there is no single solution. Even considering a percent flat tax rate doesn't provide a viable solution.
Breaking this down, and starting with property tax, one of the biggest things I see that we should be focusing on is a tax rate that is relative to two things: the impact of the property on infrastructure, and what the value of a property is. Residential property owners shouldn't be expecting to support the intense infrastructure usage of a shipping company at the port. Similarly, A small business doesn't flood the highway with trucks for shipping, and shouldn't pay 3x the tax rate that large businesses do.
Alternatively, you also have large medical institutions that have a massive impact on local infrastructure as well, while also providing a huge boon to locals with medical services and professionals. If we want to encourage doctors and medical professionals to continue to grow in SC, then we need to show that we recognize that benefit, should those institutions assist in providing it, and adjust tax rate of both the property of the medical institutions and income of medical professionals accordingly.
This same concept should be applied throughout SC and varying professions, and would balance out economically for locals, while showing that these companies, businesses, and high earning individuals care for the state that they reside in by contributing to through a tax system that benefits businesses and locals alike, simply at a much larger scale.