what is so hard about a line that says: "enter income here (all sources)_________ * x% = income tax paid." then the government can define income as: wages, tips, dividends, etc. see your first point.
taxes on goods would work the similar to how it does now. new goods are taxed, used goods are not. it discourages waste. necessities are not taxed (food).
last i checked, services weren't taxed. the services provider pays taxes on what they are paid to provide a service. i don't charge clients taxes for my professional services. though, what i have to pay in taxes are calculated into what i charge.
better, i think, if you only charge a sale tax then you get taxes from hookers, drug dealers, "rich" people buying caviar etc.
morally, i think, taxes, as a percentage, should be equal. i shouldnt pay a higher (or lower) percentage of my income because of some magic number the government pulls out of its cornhole.
however, i should be able to give the government more money if i want to. do high tax advocates do that? i havent met any that do.