Hmm.. it's a bit of a conundrum... Unless Steem gets some more real world value (beyond get more Steem to get more Steem) it could be truly considered a kind of pyramid scheme. Hmm...

However, imho the systemic solution (those are the best ones!) would be to find a way to prevent this circular positive feedback because the whole system might end up breaking down in a kind of monopolistic, robber-baron dystopia. There should be a mechanic in place which would engender a negative-feedback loop, where the more Steem you get, the harder it is (proportionally ofc) to acquire more. Not saying that those with more SteemPower should earn less than those who don't have much, just that the curve should be logarithmic rather than exponential. It should flatten down towards the right rather than steeply increase. Say, the more you have the less percentage you can earn in a month... you would still earn more in absolute terms than the less fortunate ones, it's just that relative growth of your hoard would wind down.

As you mentioned, demand drives supply - and this would actually increase demand. At the moment it's easy for those who have a lot to get even more. If you would somehow control this growth of capital, those who really need a lot of SteemPower (to promote their content for example) would actually have to go and buy it therefore increasing the price.

How to do this practically, I currently have no idea 'cause I'm still a total newb around here. I've got some experience in games and systems design though and something might pop into my head once I get a better sense of how this whole Steem system operates.