Bouygues operates in construction, telecom and media with solid cash‑flow generation, but the 2022 acquisition of around €6 bn and continued high capex (≈ €2.6 bn) have pushed net debt to about €7.4 bn and raised leverage significantly. The company’s rating headroom is now constrained, and preserving the investment‑grade rating will likely require optimizing the capital structure through equity‑like instruments. Hybrid bonds would provide the needed equity credit (≈ 50 % of the face value) while keeping the cost of debt only marginally higher. With a total adjusted capital of roughly €29.5 bn, the 11.25 % tranche corresponds to about €3.3 bn of hybrids – within the permitted €3 bn per year – and would meaningfully improve adjusted leverage and support the rating.  

**Recommended utilization:** ≈ 11.25 % of total adjusted capital (≈ €3 bn hybrid issuance over the next 18 months).

<answer>11.25%</answer>