As it's the dog days of summer and there's not much going on, I figured I'd see if anyone else has considered what sort of (realistic) new alpha abilities might work in this show, or creative ways in which current abilities could be used or altered. Maybe we can come up with something about which Shakespeare never wrote.
Rachel can increase the sensitivity of one of her senses at the expense of sensitivity of her other senses. Much like Daredevil (Marvel Comics), with her hearing Rachel could turn herself into a "bat", using her hyper-hearing for a echolocation type of effect, allowing her to move around in low light conditions or perhaps even in complete darkness.
Bill's ability has to this point only manifested itself as an increase in strength and durability. It doesn't seem to last overly long and then he's done for at least as long as he was hyped up, perhaps longer. Why does this "endocrinal fight or flight response" only manifest itself only as "fight" and not as "flight"? Why not have that adrenaline rush affect his speed in place of strength? I'm not talking comic book superhero speed, just something which suddenly puts him close to being a track star (or maybe a bit faster?) or increases his reaction speed. This would be different from the ability which Hicks possesses in that Hicks can process movement and react accordingly, while Bill would actually be moving faster. Active vs reactive.
EDIT: it gets pointed out later in the thread that Bill has moved at an increased rate of speed in the episode "Never Let Me Go".