Yet another of my pet hates is a halter neck dress. Maybe its because I am either sewing or on the computer, but my neck does not like halter neck dresses. So if I find a dress I like but it has a halter neck, I change it to normal straps. The only thing you have to do is attach the back strap closer to the centre back. The reason for this is that the halter strap at the front will be closer to the underarm, and if you put the strap in what I would call the normal position for a strap, then it will fall off the shoulder. The only issue you will have is bra straps showing, but if you where a strapless bra you would not tell.
Judith aka genie