The examples you suggest can be done on Steemit now without changing anything. And in fact, with the planned Hard Fork 17, reward splitting very possible. Doing this automatically could be done with an app. Your idea got me thinking and I ended up writing a post about it here. Thanks for that 😄

However really changing the economic model would be something quite fundamental. I think to truly do it you're talking about separating from Steem, minting a new coin, etc. Definitely possible, Golos did it, though they're still closely related.