SP as an exclusive platform acquired token, would be like Rep. You can't buy your way to Rep, so too for SP you would not be able to buy your way up the SP power ladder.
I like the way you think! Although I wouldn't narrow it to just "Reputation"because thats only one aspect of social capital.
Thanks. Hehe... nono... I was just making an analogy as to how it's acquired, i.e. you can't buy it. ;) Not that it will be the new rep.