Write a business letter addressed to the Mr. Smith evaluating the feasibility of the DTC model and its potential impact on GreenLeaf's supply chain operations. The letter should include the following: 

1. A brief overview of the DTC model and Shopify's software-as-a-service (SaaS) technology. 

2. An examination of GreenLeaf's existing capability of adopting a DTC approach given their current business model. 

3. An evaluation of the benefits and drawbacks of the DTC model for SMEs, including the potential impact on branding, data control, and fulfillment strategies. 

4. A recommendation on whether switching to the DTC model and using Shopify's software-as-a-service (SaaS) technology makes sense for the company.