The only reason not to have sliders appears to be that the Developer team wants *their* vision of what those faces look like be the ones you can pick from.
That's a terrible reason. Once the player gets the game, the developers no longer have a say in how that content is consumed.
The creative element in RPGs is a collaborative effort between the developers and the player. The devs should not be trying to protect the player from himself.
Im not implying ill intent here, and i guess implementing sliders isnt as easy as implementing whatever user interface the devs use since its probably not fit for purpose for the end user.
Sliders are definitely more work, so I can see why they're not included yet. I won't judge the game for its lack of slides until full release, but even then games rarely offer as much customization as players would like. Just look at Skyrim and how much more detailed the character creator has been made with mods.
I just read an article that addressed this on Kotaku. They are planning on adding different heads already in the game to different body rigs, add new faces and new hair options throughout EA.
I'm already genuinely impressed by the hair options.