I agree with your mod path of adding STi parts, mainly because they 'should' be covered under warranty. Don't forget Subaru also sells performance add-ons under SPT.
As far as the stigma: one would think the BRZ audience is more mature than the "oh you couldn't afford the real thing" mentality of some of the WRX STi people you mentioned.
But that's just hopeful thinking on my part. I hate when people ask me, "Is that an STi or 'JUST' a WRX??"
