Sovereigns self-insure via reserve accumulation, prioritizing liquidity over yield. This practice imposes opportunity costs and can amplify the convenience premium on traditional reserve assets. This paper evaluates Synthetic Reserve Deposits (SRDs), a pooling mechanism designed to improve the return-liquidity trade-off. Participants would hold floating-value claims on a vehicle comprising a settlement buffer, an investment portfolio, and, in some designs, an optional collateralized liquidity window. The architecture separates the allocation of portfolio risk from the provision of short-term foreign-currency liquidity: market risk remains with SRD holders, while liquidity is provided through redemption at contemporaneous executable value or through secured advances. Simulations illustrate that the structure can shift the return-liquidity frontier outward under explicit downside-risk constraints. General equilibrium modeling suggests that, if implemented at sufficient scale and under appropriate conditions, reallocating reserve demand through this mechanism could increase the effective supply of reserve claims and affect the global financial cycle, creating aggregate welfare gains and possibly Pareto improvements depending on initial global asset positions.