I like kits that don't have needles- I already have all the needles I need. A beginner may want them though. I also like kits that have all the"extras" like whatever buttons, ribbons, trim you need to make the finished product REALLY look like the picture.
A good picture and/or sample of the finished item goes a long way.
I like kits where the pattern isn't something I'd find readily on line- or a kit for a specific item from a special magazine article. Ususual yarns help too. and as awlays a clearly written pattern is important.
if it is in a nice shop (not a JoAnns or something)- I want to be able to look at and feel the yarn- don't just shove it in a plastic bag for me to guess what it will feel like. (I bought a "kit" for a blanket for more money than I had planned because the yarn was just that irresistable, and the blanket ADORABLE: it came in a little plastic basket, with yarn, pattern, ribbon, and a the pattern had a list of a range of yarns that could be used later if you wanted to make it again)
To have a range of kits for a range of abilities may be difficult- most kits I seem to find in shops are for the absolute beginner, with the most basic pattern.
I'm so glad you asked! I bet you will get a lot of ideas... MKZ