I'll analyze Bouygues' financial position and capital structure to determine the appropriate reliance on hybrid bonds.

## Key Financial Observations

**Leverage and Debt:**
- Net debt surged from €941M (2022-01-01) to €7,440M (2023-01-01) — a massive increase largely driven by acquisitions (€6,269M cash used in obtaining control of subsidiaries, likely the Equans acquisition)
- Long-term borrowings nearly doubled from €5,805M to €11,586M
- Total equity is €13,932M, so net debt/equity ratio went from ~7% to ~53%

**Profitability:**
- Revenue grew from €37.6B to €44.3B (+18%)
- Operating profit (recurring) improved from €1,693M to €1,962M
- Net income declined from €1,305M to €1,131M, partly due to negative equity method results (-€30M vs +€222M)
- The company remains solidly profitable with adequate cash generation (€2,978M operating cash flow)

**Credit Profile:**
- Bouygues is an investment-grade company (typically rated A-/BBB+ range by rating agencies)
- The significant increase in leverage from the Equans acquisition creates a need to optimize the capital structure
- The company has diversified operations (construction, telecom, media, energies & services)

**Hybrid Bond Considerations:**
1. **Rating protection:** Bouygues' leverage jumped significantly. Hybrid bonds receive partial equity credit from rating agencies (typically 50%), which helps maintain investment-grade ratings without full dilution to equity holders.

2. **Market conditions:** The 2022 swap curve shows rising rates (5Y at 1.726%, 10Y at 1.927%), and corporate bond spreads widened. The sub-senior delta of 0.2 (20 bps additional spread for subordinated vs senior) is relatively modest, suggesting hybrid issuance is not prohibitively expensive.

3. **Post-acquisition deleveraging:** After a transformative acquisition like Equans, companies commonly use a mix of instruments. Hybrid bonds are a standard tool for large French corporates (Bouygues has historically used them).

4. **Size and profile:** Bouygues is a large, diversified conglomerate with stable cash flows — a good candidate for hybrid bonds, but not exclusively so.

5. **Balance:** The company needs primarily senior debt for its core financing (evidenced by the large increase in long-term borrowings), but a meaningful hybrid component helps with rating metrics. However, going entirely or predominantly hybrid would be inefficient and costly.

**Conclusion:** Given the significant leverage increase from acquisitions, the need to protect the investment-grade rating, the manageable subordination premium, and Bouygues' profile as a large diversified industrial group, a moderate allocation to hybrid bonds (around 25% of the capital structure optimization) is appropriate. This reflects the common practice of using hybrids as a complementary tool rather than a primary funding source.

<answer>25%</answer>