Trousers in different waist fits. Adjustable ones are ok, but for real skinny minnies you end up with a huge bulge at the sides which isn't comfy and looks naff.
I second warm, practical coats for girls.
I also second modern clothes for 7yrs plus that aren't mini adult clothes or branded.
Toddler and pre school girls clothes in non pale colours. Bright and stain-resistant is good!
Shorts for toddler boys that are slim, not huge combats that look daft with a pair of twiggy legs!
Clothes for mums especially designed to hide the belly. Don't care what else they do, but nice tops and trousers that are specifically designed to minimise the post baby 5-month-pregnant look.
Macs for girls that are thicker than pac-a macs, but not as thick as ski jackets. Mothercare used to do them, but no more.
Hats with two sets of matching gloves for when one gets lost...
All these need to be reasonably priced of course - no more than M&S prices...
Erm, that's it for now