Although I would prefer ANH Leia as well, I can see why this version would get the attention early on too. With all the costuming, pop culture references, etc. to Slave Leia...it could be argued that it is almost as iconic as well. Plus, I can see them mixing it up.
As for the rest of the lineup (and Greedo in particular), they seem to be setting things up hoping for a longer running line. As someone who has bought Marvel Legends (as well as DCUC), you often times had to wait several waves (even years worth) to complete teams, or even get to some of the more well known characters. If they front loaded the Black Series with ANH Luke, Han, Leia, Chewie, 3PO, Vader, Stormie, R2, etc. then it really makes it more difficult for them down the road to come up with popular waves. I remember with Marvel Legends (back in the Toy Biz days) one of the first waves had Toad in it alongside the likes of Cap, Iron Man, and others. Toad. But, they eventually got to them. I'll admit, ideally I'd like Chewie (to go with Han), 3PO (to go with R2), and Vader right away (Vader is the most surprising wait to me), but I can understand why they are spacing things out.
They also seem to be somewhat spacing it out among the movies too. Continuing lighter on the prequel stuff, and then taking a couple from each OT movie. Definitely looking forward to seeing pics of all this though, probably at SDCC I'm guessing.