I figured it out after I wrote the reply. A cap would be a communistic approach, I still like the idea.
The only and strictly quantitative discriminating factor between accounts is the amount of SP they hold or have command over.
What about your reputation? I think there should be another possibility of gaining more influence on the platform than throwing money into your account. I have no idea how it should work but I feel the duration of your participation and your activity should be appreciated in a certain way.
Also, promotion of Steemit should be valued. Let it be referrals, view counters from non Steemit users or another concept.
Thanks for your reply (: