As a former employee of one of those large investment banks who traveled quite a bit, it's true that FS offers good pricing vis-a-vis the published rates on their website - however, in my experience price was never below what you could find online by hustling a bit with kayak and the like.

With that said, in theory whether your find a friend who books it for you or not should not make any difference, because the agreement is that only employees of the bank are allowed to stay at those rates, regardless of who puts through the booking (i.e. they should check status of client at check-in to make sure it's an employee of the firm).

In practice however, when booking FS (or MO, Rosewood, etc) using my work email, I have never been asked for confirmation of employee status at check-in.