Most people know who Sinestro is because of the Super-friends makes sense to have him "front and center" as the big bad in some capacity at least Parralax was only an excuse to have Jordan go rogue and then was retconned into some fear monster, but what do we really know about it? not much really and from what i've seen the movie didn't even try.
I'm not against using Hector Hammond in the movie especially if they would have had deleting Parralax and tied Sinestro and Hector together somehow.
I'm thinking Sinestro could have used Hector to attack Hal either because he hates earthlings and doesn't trust us or as a way to test Hal to see if he was truly worthy.
I also liked the comic book origin where he was dissecting Abin Sur and something happened to him although it could even work out that he got something off Abin Sur or his ship on purpose that gave him powers and possibley go mad.