You seem to want to put the most pressure on the middle rather than where it belongs---on the top.
Why does it belong at the top? It's YOUR job that's threatened by low wages, so why don't you bear any responsibility for the solution? Putting the blame on somebody else and expecting somebody else to pay is what caused the problem in the first place.
In my mind, you would advocate pressure more on the 15% to share their wealth before even addressing the 5% with the lions share.
How do you propose to "address" the ones with the lions' share? They can spend a lot of money on accountants and lawyers to avoid paying. Why should we spend more money on our own accountants and lawyers to try to get them to pay more? It's just a vicious circle.
The sensible solution is for the people who use the services to pay for them. Why is it such a bad idea to help them be able to pay?