I think the larger question is the implication that (assuming we moved to a purely wealth tax), there's a minimum rate of return on wealth - this is already functionally true, but it sets an interesting floor to the return on investment for an asset.
I'm by no means a financial wizard, I'm sure there are huge flaws in the idea I can't see after an hour's thought, I was just playing with the idea, but it seems like it solves a lot of the problems inherent in income taxation - different entities (people, corporations, foreign investors, etc) being taxed at different rates, the relative spending ratios of various income brackets, etc.
It follows essentially a similar line of thought as the land value taxes, except of course applying to all assets.