Bouygues has a clear but not overwhelming rationale for considering hybrids.

Key considerations:

- **Starting point / precedent:** Bouygues had **no hybrid bonds outstanding** and has **never issued hybrids**. This is a strong negative signal under the guidance, because prior non-use usually indicates management, investor-relations, rating-agency, or cost reasons not to rely on hybrids. This argues against a high recommendation.

- **Leverage deterioration:** Net debt increased sharply from **€0.9bn to €7.4bn**, largely reflecting major acquisition spending, with **cash flows used in acquisitions of about €6.3bn** and investing cash outflow of **€8.6bn**. S&P Net Debt/EBITDA of **3.26x** and FFO/Net Debt of **24.5%** indicate materially tighter credit metrics than the prior year. Moody’s adjusted leverage trend is also described as **deteriorating**. This supports some hybrid use to restore rating headroom.

- **Funding needs:** The group has sizeable debt: long-term borrowings rose to **€11.6bn**, and current borrowings/current portion of debt were **€1.36bn**. However, liquidity remains substantial, with **cash and equivalents of €5.7bn**, and operating cash flow of about **€3.0bn**. Funding pressure is meaningful, but not clearly extreme or transformational over the next 18 months beyond the acquisition already completed.

- **Business profile:** Bouygues is diversified across construction, telecoms, media and services, not a pure regulated utility or highly predictable infrastructure issuer. This makes hybrids potentially helpful for balance-sheet optics, but less obviously central to preserving an “A”-type regulated infrastructure profile.

- **Cost environment:** Market rates increased sharply in 2022. The 5Y–10Y swap curve moved from near-zero/negative levels in 2020–2021 to around **1.7%–1.9%** in 2022, while subordinated/hybrid spreads also rose. A new hybrid would likely be meaningfully more expensive than Bouygues’ legacy senior debt. This reduces the attractiveness of large-scale issuance.

- **Potential rating benefit:** A moderate hybrid issuance could receive partial equity credit from S&P and improve adjusted leverage metrics. But given the absence of previous hybrids and the higher cost of capital, the case is more about **limited rating flexibility** than a need to maximize equity credit up to the 15% cap.

Overall, Bouygues’ leverage deterioration and acquisition-related debt increase justify **some** hybrid consideration, but the company’s lack of prior hybrid issuance, still-solid liquidity, and materially higher hybrid funding cost argue against a large allocation. The most balanced recommendation is therefore a **low-to-moderate use of hybrids**, consistent with **3.75% of total adjusted capital**.

<answer>3.75%</answer>