To determine the appropriate extent to which Bouygues SA should utilize hybrid bonds, we need to analyze its capital structure, leverage metrics, and funding needs based on the provided financial data for the fiscal year ended December 31, 2022.

**1. Leverage and Credit Metrics:**
Bouygues experienced a significant increase in its net debt, jumping from €941 million in 2021 to €7.44 billion at the end of 2022. This increase is primarily attributed to a major acquisition (indicated by the €6.27 billion cash outflow used in obtaining control of subsidiaries, which corresponds to the strategic acquisition of Equans). 
Despite this large debt-funded acquisition, the company's leverage remains remarkably comfortable. If we approximate the operating EBITDA by adding back D&A (€2.23 billion) and right-of-use asset depreciation (€446 million) to the recurring operating profit (€1.96 billion), the EBITDA sits comfortably above €4.6 billion. This translates to a Net Debt / EBITDA ratio of around 1.6x. This robust ratio suggests no significant leverage pressure, allowing Bouygues to easily preserve its strong "A" range investment-grade rating without needing structural enhancements like hybrid bonds.

**2. Capital Structure and Cost of Debt:**
Bouygues' current capital structure relies on regular senior debt (long-term borrowings of €11.59 billion) and equity (€13.93 billion). The company currently has no outstanding hybrid bonds. Given the prevailing market data for 2022 (e.g., higher swap rates and a widening subordinated-senior delta yielding a premium of ~230 bps for sub-senior non-financial IG bonds), issuing hybrid bonds would materially increase Bouygues' currently low, highly optimized cost of debt.

**3. Refinancing and Strategic Needs:**
While 2022 featured a transformational acquisition, the M&A transaction has already been completed and successfully absorbed by existing cash and new senior debt facilities, with no signal of further extraordinary capital requirements moving forward. Bouygues faces low future refinancing needs that threaten its credit metrics.

**Conclusion:**
Because Bouygues maintains exceptional leverage metrics (Net Debt/EBITDA < 2.0x), holds a strong "A" range rating, has no outstanding hybrids, and would face an unnecessary increase in its cost of capital if it were to issue them, there is no rationale for hybrid issuance to stabilize its trajectory or preserve its rating.

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