To a large extent, this already happens.
Steemit Inc delegates over 13m Steem Power out to the content creation platforms (dApps) that operate on the Steem blockchain.
The delegation is made through the misterdelegation account. This includes (but is not limited to):
These content creation (or task-orientated) dApps then reward their users, generally based on the recommendations of some kind of moderation team or wisdom-of-the-crowd information.
The moderation approach removes the need for a whitelist. A whitelist approach could reduce quality if users became complacent once they made it onto the whitelist. It could also be perceived as unfair and potentially lead to lots of arguments as to who should be on the whitelist.
I think that continued expansion of this amount of delegation to new platforms would be beneficial. However it needs to be remembered that there is only so much in rewards to go around. There thus needs to be a balance between Steemit Inc funded rewards and rewards generated by other SP holders and investors.
A sudden increase in Steemit Inc funded rewards would result in a sudden decrease in rewards generated by all other users. So the process delegation process should proceed gradually and only be given to the best platforms.
But broadly I think that this fulfils the same aim as your suggestion, just with a little more control and fairness.
Steemit doesn't care much about content creators but investors. though steemit is a blogging social platform, it doesn't care much about how good a content creator you are if you don't invest any physical cash into the platform. So expecting steemit to dish out huge $10 worth of upvote to retain or encourage good content creators is a wishful thinking
Steemit is thinking on how to retain it's investors and even thinking of ways to cut the 75%reward content Creator's are getting on their blog to give to investors so that they can keep leaving their money on the system. One thing they are forgetting is that, without the content creators steemit will be a ghost town and investors will be scared to leave their money in a ghost town.