The main issue of steemit is that it's way more profitable and less time consuming just to self-upvote and abuse the system (for anyone holding SP). The only way I see this change is when a lot of SP from the devs is being used to both reward good users and punish scammers.

It would be nice to see the SP being delegated to all kinds of honest projects that both keep Steemit clean and encourage good behavior or form strong communities. I really like how the busy votes are being spread and it would be nice to have something similar like you suggest.

I would not set a maximum SP though, one of the issues for bigger accounts is that it becomes increaingly difficult to beat the 10 daily self-upvotes since the amount of even bigger accounts that give support is very limited. (which is needed to beat the 10x selfvote number).