To determine the extent to which Bouygues SA should rely on hybrid bonds in its capital structure, we must evaluate its financial position based on the 2022 annual report data:

1.  **Financial Stability & Debt Profile:** As of the end of 2022, Bouygues has a significant net debt of 7,440,000,000 EUR (up from 941,000,000 EUR in 2021). The long-term borrowings have increased substantially (from 5,805,000,000 EUR to 11,586,000,000 EUR), indicating an increased reliance on debt.
2.  **Market Environment:** The market data shows a sharp increase in interest rates (Swap Curves 5Y, 7Y, and 10Y all shifted from negative/near-zero in 2021 to ~1.7%-1.9% in 2022). Furthermore, the iBoxx EUR Non-Financial IG spreads have widened significantly (from 1.298% to 2.295%). 
3.  **Rationale for Hybrid Capital:** Hybrid bonds provide "equity-like" features (often receiving partial credit from rating agencies) that help support a credit rating while financing growth or acquisitions. Bouygues underwent a large acquisition (reflected in the massive increase in goodwill from 7.4 billion EUR to 12.6 billion EUR and increased cash outflows for acquisitions). 
4.  **Conservative Capital Allocation:** While hybrid instruments are useful for leverage management, they are expensive compared to senior debt. Given the company's strong revenue (44.3 billion EUR) and ability to generate significant operating cash flow, it maintains a robust, investment-grade profile. Over-relying on hybrid capital (e.g., 50-100%) would be inefficient due to higher coupon costs. However, some usage (25%) acts as an effective tool to manage the debt-to-equity ratio during periods of high acquisition activity and rising interest rates. A 0% allocation would ignore a useful tool for capital optimization, but higher levels (50%+) would overly dilute the cost of capital. A 25% allocation balances the need for financial flexibility with fiscal prudence.

<answer>25%</answer>