Evaluate the effectiveness of three different founder succession system models (Model A: Internal promotion, Model B: External hire with mentorship, Model C: Gradual handover with phased retirement) for a hypothetical mid-sized SaaS company with 50 employees and $5M annual revenue.  Consider factors such as employee morale, financial stability during transition, knowledge transfer efficacy, customer retention rates, and long-term business growth trajectory (3-5 years post-succession).  For each model, outline the potential risks and benefits,  provide a detailed timeline for implementation, and estimate the financial implications.  Finally, compare the three models across these factors and provide a reasoned recommendation for the optimal approach, justifying your choice with specific data points and projections.  Present your findings in a structured report with clear headings, subheadings, data tables, and concise conclusions.