Assess current cross-channel performance for [Company] over [Timeframe] and recommend a budget reallocation plan that maximizes marginal ROAS while meeting a blended [ROAS_Target]. Use channel-level data for [Channels] including spend, revenue, impressions, clicks, and conversion rate. Identify diminishing returns by estimating response curves and compute the shadow price (incremental revenue per incremental £) for each channel. Reallocate within a [Budget_Ceiling] and enforce minimum viable spend thresholds to maintain learning phases. Provide risk flags for volatility, learning resets, and seasonality conflicts.
Output format: Return a markdown table with columns: Channel | Current Spend | Proposed Spend | Δ Spend (£) | Marginal ROAS | Expected Incremental Rev | Risk Notes | Guardrails. Follow with a 150-word narrative summarizing trade-offs and contingency triggers.