Here some thoughs on:

Reputation

In terms of reputation, we do not have to look far way to see that (besides the algorithmically calculated score) there is an even better indicator which is already in place - and also used as a main indicator in popular social networks: the number of followers. In fact, people usually follow other people if they like their content, if they are really interested in reading, watching or earing what they post. Accounts with a high number of followers are more likely to be read by more people. These are in fact the most valuable accounts in terms of advertisement and product placement. Perhaps, to spin around your though-experiment, the blockchain should automatically reward post proportionally to its author's number of followers in the same way, for instance, a youtube partner pays more to a user with more followers, or an advert cost more on a newspaper with a higher number of printouts.

In terms of user growth / user retention, in my opinion, there is only one way: improve the user experience: And this, can only be achieve by equalky improving the site's a) Usability and b) Customisation

Usability
Steemit.com, which is today almost the only trustable face of the steem network, is far behind sites/apps such as facebook, youtube, tweeter in terms of usability. It is not easy to create content for steemit and it is even more difficult to discover it. Add picture/videos upload capabilities, album creation & sharing, chating, grouping, linking, easy editing and formating and more interation capabilities. Create a full featured profesionall phone app, comparable in terms of performance and functionality to those from youtube, facebook or tweeter and the user base will automaticallt begin to grow.
And the investors will follow and they'll also buy liquid steem to pay content creators with a high number of followers for their content

Customisation
People love to be unique. They love to have differenciating characteristics To buy clothes, houses or cars which have a personal touch. Do you remeber the product launch of the apple watch? What was the key of its success?
Bloggers like to personalize their blogs and they articles. Youtubers love to create their videos with a clear, differenciating and personal style and so they do with their entry pages. And so do twitter and even facebook users.
Add customizacion capabilities to help users create appealing personal identities. Im sorry but a link to a url as a profile picture is just not enough.
Customisation will atract users to the platform. I'll happen.

I seriously think, we shoud become less concerned about steempower and steem economy and investors in general and beging thinking more about the users who use the site/app/network/blockchain because they enjoy it