The biggest impact from self-voting isn't in the few dollars that your own self vote awards you but rather in the additional exposure that such self-voting achieves.
This is only true for posts (not comments), and only while the option is available. If it were to be taken away, or even cost more, the advantage of high SP holders to promote their posts would diminish. Now this divides people into two camps, but you'll find a lot of support here for the camp which thinks that good posts are not necessarily written by the rich and famous. If you want to promote posts a rich person you can always put your SBD down and hit the Promote button.
I don't know about your two flavors of Steem argument. You may be right, in that now we have opened the pandoras box of effective self voting (do not forget it was not worth it before several weeks ago) we cannot close the lid on it now that everyone, especially high SP holders, have had a taste of super charged self vote rewards.
The utility of SP on the platform would certainly be worth diminished by any blockchain change which either removed self voting or disincentivized it. However ostensibly that is exactly what HF 19 intended to do - allow minnows greater power, and when balanced diminished the voting power of whales. It was seen as good because it was seen as good for the platform as a whole.
The value of SP is really the value of Steem which I don't agree is as simply put as you claim and I agree with Luke Stokes in his comment here, with many variables and moving parts beyond self voting. But I don't think it's given that removing a large advantage over minnows will drive adoption and investment.