A sartorial modification may make a garment more suitable for the person, but requires a technical evaluation. The possibility of intervention depends on the product and the necessary processing. The service should help the customer understand what can be changed and with what consequences.
On the commercial level, I propose to discuss intervention, cost and time before the purchase. The information must come from those who can evaluate the work. A generic promise of adaptation can create expectations that the structure of the garment does not allow to meet.
In a hypothetical example, shortening a sleeve can change the ratio of cuff to decorative detail. The client should be able to assess this effect before deciding. The comparison concerns the predictable outcome, avoiding presenting each intervention as simple or reversible.
Final delivery requires verification consistent with what is agreed. The conditions of the service must be properly defined. The change adds value when it makes the product more suitable and remains understandable as a specific job, with possibilities and limits clarified during the choice.