What a bespoke blazer does that a ready-made one cannot
The primary benefit of a bespoke women's blazer is fit. Women's ready-made blazers are made to one of a handful of standard body proportions. If your shoulder width, bust, waist and torso length happen to correspond to one of these standards, you may find a ready-made blazer that works. Most women do not, because most bodies do not match standard sizing in all four critical areas simultaneously.
A bespoke blazer is made from your specific measurements. The shoulder sits precisely where your shoulder ends. The chest buttons without pulling. The waist takes in to your actual waist. The length finishes where you need it to finish for your trouser or skirt length. These are small differences that produce a very large visual effect.
In cloth, a navy or charcoal blazer in a lightweight worsted is the most versatile first choice. It works with everything and lasts indefinitely. A brighter or more textured cloth — a glen plaid, a fine check, a linen — is a more personal second or third blazer that adds colour and character to the wardrobe.