Sightstone on Riven?

Bare with me here because I'm fairly certain most people would think that's dumb but I had a thought. I don't really play Riven much but I played a few matches the past week or so because I do find her fun from time to time and I just had a match where I noticed I spent a lot of time thinking "I could do this, but the map is dark there and my trinket is down." So I played with the idea of getting a Sightstone. Didn't actually do it, but considered, and I think Riven has a surprisingly strong case for building it on what is usually considered a carry Champion.

There's no arguing that having an infinitely refreshing supply of wards is good on everyone, it's a matter of "is it worth it to drop an entire other item for this weird rock with an eyeball in it" and I think on Riven in may be a yes. Consider: Riven is a fighter/skirmisher and flanking is important, and wards make flanking significantly easier and safer. 500 hp (once upgraded)helps make her more survivable which is great since her big weakness is being very squishy for a fighter, and even Cleaver only gives 300h. There's also no arguing SS is one of the most cost-effective items in the game. On top of that, Ruby also gives that unique CDR for item actives, and and are standard items on her.

I think a 6-item build with RSS in it would look something like . Am I on to something or is it not worth giving up the 6th slot?