I like your approach. I think a reason why a lot of people resist the idea is that they're afraid of losing what they have. No working-class person should lose their nest egg in order to redistribute the wealth. Nor do any need to. Because the problem isn't the middle class or even the upper-middle class. The problem is the upper-upper class, the owner-caste, the plutocrats, the zaibatsu, the financial oligarchs.
So when we talk about it, our rhetoric needs to highlight that we're not after any doctors or lawyers or professors emeritus. Those aren't the people siphoning and hoarding the lifeblood of society; they're not the ones who are appropriating the surplus value of labor in order to generate exorbitant personal wealth to the detriment of everything and everyone around them.
We need to communicate better about working-class solidarity, and how that includes the middle classes, yes, even up to and including the upper-middle class. They can keep their mcmansions and their corvettes. That's not the means of production that needs to be seized.
Personal possessions are fine. It's privately-owned business empires that need to die. And the "public" stock market should be nationalized, and governed by democratic civil institutions, like a hybrid between a union and a bureau, or something along those lines.
Especially–and starting with–public utilities and other infrastructure, which honestly needs to include communications infrastructure such as cell towers & satellites, internet, and even social media. But there I'm starting to get a little radical, and I don't know if the broader social conscience is ready for that leap quite yet. The key idea is that these things should be treated as public goods rather than commodities to be exploited for profit by individuals or business entities.
And yeah, there definitely needs to be an upper wealth limit. $100 million seems reasonable. You reach that, you win. Nobody needs more than that, so at any point if a person's net worth goes over it, every dollar over should be taxed at 100%.
I'd caution against applying wealth tax to anything under that limit though, because the thing about wealth is that it's a static amount unlike income, so a recurring wealth tax would actually tax the same wealth redundantly. So it's probably best to only apply it to any amount over the upper limit.
And lastly, but arguably most importantly, capital gains need to be taxed more fairly. Currently, in the US at least, the highest tax bracket for capital gains is taxed at a rate comparable to the income tax bracket of about a $40,000 salary. It's so bullshit.