Architected a Series-A financial model sheet by sheet with the ARR bridge and error checks spelled out

You are a VP of FP&A at a top-tier company. Help me design a robust financial model structure with clear assumptions, driver-based formulas, and scenario capabilities.\n\nCOMPANY/STAGE: {{company_description — e.g., 'B2B SaaS, $5M ARR, 50 employees', 'D2C e-commerce startup, pre-revenue'}}\nMODEL PURPOSE: {{purpose — e.g., 'Series B fundraising', 'Annual budgeting', '5-year strategic plan', 'Unit economics analysis'}}\nMODEL TIME HORIZON: {{forecast_period — e.g., '3 years monthly', '5 years annual'}}\nKEY STAKEHOLDERS: {{who_will_use_this_model — e.g., 'Board, CFO, department heads'}}\n\nCURRENT FINANCIAL DATA (paste any available data — P&L, balance sheet, metrics):\n{{financial_data}}\n\nOUTPUT — Financial Model Architecture:\n\n## 1. MODEL OVERVIEW & DESIGN PRINCIPLES\n- Model type: [3-Statement Integrated / SaaS Metrics / Unit Economics / LBO / DCF]\n- Granularity: [Monthly / Quarterly / Annual] with roll-ups\n- Scenarios: [Base / Upside / Downside] + sensitivity tables\n- Key design principles: [Separation of assumptions from calculations / Modular structure / Error-checking / Audit trail]\n\n## 2. ASSUMPTIONS HIERARCHY\nOrganize all assumptions by category with sources and confidence levels:\n\n### Revenue Assumptions\n| Assumption | Base Case | Upside | Downside | Source | Confidence | Driver Formula |\n|------------|-----------|--------|----------|--------|------------|---------------|\n- Pricing/MRR per customer\n- Customer growth rate (new acquisitions)\n- Churn rate (logo and revenue)\n- Expansion/upsell rate\n- Sales cycle length\n\n### Cost Assumptions\n| Assumption | Base Case | Upside | Downside | Source | Confidence | Driver Formula |\n|------------|-----------|--------|----------|--------|------------|---------------|\n- COGS / Gross margin structure\n- Headcount plan by function\n- Compensation assumptions (base, bonus, benefits)\n- Marketing spend and efficiency (CAC)\n- Infrastructure/hosting costs\n- Rent, tools, other OpEx\n\n### Working Capital Assumptions\n- DSO, DPO, DIO\n- CapEx requirements\n- Depreciation/amortization schedules\n\n## 3. MODEL STRUCTURE — SHEET-BY-SHEET\n\n**Sheet 1: Dashboard**\n- Key outputs summary (KPIs, charts, scenario selector)\n- Executive summary metrics\n\n**Sheet 2: Assumptions**\n- All inputs in one place, color-coded (blue = hardcoded)\n- Assumption validation checks\n\n**Sheet 3: Revenue Model**\n- Build-up by segment/product\n- Customer cohort waterfall (if SaaS)\n- ARR/MRR bridge: Beginning + New + Expansion - Churn - Contraction = Ending\n\n**Sheet 4: Headcount & OPEX**\n- Headcount plan by department and role\n- Fully loaded cost per employee\n- Hiring timeline\n\n**Sheet 5: P&L**\n- Revenue → Gross Profit → EBITDA → Net Income\n- Month-by-month and annual summaries\n- Variance analysis framework\n\n**Sheet 6: Cash Flow**\n- Operating, investing, financing cash flows\n- Cash balance and runway calculation (if applicable)\n- Free cash flow bridge\n\n**Sheet 7: Balance Sheet**\n- Key assets, liabilities, equity\n- if applicable for stage\n\n**Sheet 8: Metrics & SaaS KPIs** (if SaaS)\n- ARR, MRR, NRR, GRR, CAC, LTV, LTV:CAC, Payback Period, Magic Number, Rule of 40, etc.\n- Benchmark comparisons (if available)\n\n**Sheet 9: Scenarios & Sensitivities**\n- Data table for 2-variable sensitivity analysis\n- Scenario comparison waterfall\n\n## 4. KEY FORMULAS & LOGIC\nFor each major line item, specify:\n- Formula logic (in pseudo-code)\n- Dependencies on other sheets\n- Common pitfalls to avoid\n\n## 5. ERROR CHECKING & VALIDATION\n- Balance check: Does Balance Sheet balance?\n- Cash check: Does Cash Flow reconcile with Balance Sheet?\n- Sanity checks: Are margins, growth rates, ratios within reasonable bounds?\n- Audit formulas to include\n\n## 6. SCENARIO DESIGN\n\n**Base Case** (60% probability): Key assumptions and resulting outputs\n**Upside Case** (20% probability): What drives outperformance?\n**Downside Case** (20% probability): What drives underperformance?\n\nSensitivity tables:\n| | Optimistic Input | Base Input | Pessimistic Input |\n|----|----|----|----|\n|Optimistic Other | | | |\n|Base Other | | | |\n|Pessimistic Other | | | |\n(Show key output metric in each cell for 2 most impactful variables)\n\n## 7. MODEL GOVERNANCE\n- Update frequency and ownership\n- Version control protocol\n- Distribution and access rules\n- When to revisit assumptions (trigger events)