We need to tax unearned income at the same rate as employment income and drop the National Insurance charade.
We need to increase the rate of capital gains tax to the same as income tax levels.
The main "loophole", as someone called it, used by the rich is to not take dividends and sell the company to pay capital gains tax at 20%. This doesn't show up in any widely published income or earnings stats that i know of.
Scotland isn't any poorer than the UK as a whole and has plenty of rich people, valuable companies and natural resources that can pay for public services.