Bouygues Group in 2022 shows strong scale and diversified asset base, with Equity at 12.212b and Net Debt 7.44b, giving a substantial equity cushion but still a high absolute debt level given total adjusted capital (equity + adjusted debt). The hybrid instrument cap per S&P is 15% of total adjusted capital. Current hybrids outstanding not disclosed here; assume exists some level, affecting incremental headroom.

Key observations:
- 2022 net debt fell to 7.44b from 0.94b prior year, but total assets 60.6b; equity 12.1b; leverage still moderate, debt driven by large capex in Construction/Telecom/Media mix.
- No explicit need for aggressive refinancing visible; cash flow from operations ~€2.98b, capex €2.63b; free cash flow decent but high investment pace continues.
- By rating methodology for diversified groups with high capex, hybrids can provide ballast to adjust leverage, especially if EBITDA/FCF is relied upon to service debt.

Guided by the checklist:
- 0%: Not suitable if there is any capex pressure or refinancing need; Bouygues has significant investments and debt dynamics; thus 0% would be too conservative.
- 3.75%: Moderate funding needs; possible but Bouygues likely has more leverage headroom given large adjusted capital base; hybrids could help but not essential.
- 7.5%: Moderate refinancing/acquisition needs; hybrid issuance would meaningfully improve adjusted leverage and provide rating headroom; fits if capex intensity remains high and need to preserve investment-grade metrics.
- 11.25%: High capex intensity; significant leverage pressure; but does Bouygues require that level? Possibly during 2023-2024 if capex stays elevated. However current 2022 metrics show solid cash flow; not immediate urgent.
- 15%: Very high refinancing needs; transformational capex/M&A; material downgrade risk without hybrid support; hybrid cost aligns with debt cost.

Given 2023-18 months horizon and current metrics, likely need not extremely aggressive hybrid issuance; moderate to modest headroom is prudent. Therefore I would choose 7.5% as balanced: it supports mid-term capex with leverage improvement while not over-relying on hybrids, preserving rating headroom.

Final answer: <answer>7.5%</answer>