That's a very nice looking model. As for changes, we would need to have the two LED holes left open and space inside for electronics. I think the main plate and rim should be one piece, but the separate buttons is great, it'll make it easier to use the real cell phone button to get the accurate chromed look.
The thing is though, the parts can't just be 3d printed, I think they really need to be cold cast aluminum (main body) and black onyx resin (oval buttons). You mentioned via PM to Rex that you could do cold cast, what might be the price for that, and minimum number of casts that would need to be done?
Your model looks mostly perfect, the only thing left is scaling, right? Or did you already do that? If so, what are the dimensions so I can figure out what size to make my wrist strap and start working on it?
The leather I've got for my strap matches up to the picture of Jack's VM, not the Doctor's. It's a lighter color. IF (and I say if because I don't know exactly how much time I'll have, I still want to do the run of River diaries later this summer), but IF I do a run of wrist straps I'll have to get more leather anyways and I can pick up something darker.
Oh, and there is something between the inside and outside layers of leather on the flap, but I don't know what it is. The inside has the recessed area, but the outside just ramps up to a larger thickness with no definition. I could do it with tooling leather, but I don't have a clue what the real one has in it.
EDIT: Also, on the 3d model, the part that sticks out with the LED in it sticks out at an angle, not straight up, the sides are slanted.