To determine the optimal utilization of hybrid bonds relative to the S&P Global Ratings' cap, we must analyze the company's cost of capital. 

Hybrid bonds are structural financial instruments that sit between senior debt and equity in the capital structure. Because they are subordinated to senior debt but senior to equity, their cost is typically higher than that of regular debt but lower than the cost of equity (Ke). For a WACC-minimizing firm, substituting expensive equity with cheaper hybrid debt lowers the overall Weighted Average Cost of Capital (WACC). 

S&P Global Ratings allows companies to receive equity credit for hybrid bonds up to a cap of 15% of their total adjusted capital (Total Debt + Equity). Because the cost of a hybrid bond (which can be estimated from the ISHARES CORE EURO CORP BOND yield plus the SUB-SEN DELTA, equating to roughly 3.38% for 2022) is consistently lower than the company's cost of equity, it is financially advantageous to replace equity with hybrid capital as much as possible without losing the rating agency's equity credit. 

Therefore, to minimize its WACC while maximizing the structural benefits recognized by S&P, the company should fully maximize this allowance and utilize the cap completely.

<answer>100%</answer>