Combine the rice vinegar, 0.5 cup water, granulated sugar, garlic, ginger, crushed red pepper flakes, and kosher salt in a small saucepan. Bring to a simmer over medium heat, stirring until the sugar dissolves, 3–4 minutes.
In a small bowl, whisk the cornstarch with 2 tbsp water to make a smooth slurry. While the sauce gently simmers, slowly drizzle in the slurry, whisking constantly. Cook until the sauce thickens, turns glossy, and large bubbles break slowly, 2–3 minutes.
Remove the pan from the heat. Whisk in the soy sauce and unsalted butter until fully melted and emulsified, 30–60 seconds.
Stir in the lime juice. Let the sauce stand 5–10 minutes to thicken slightly, then use warm to coat 2–3 pounds of freshly cooked wings, tossing until well glazed. Or cool completely and refrigerate in a sealed jar for up to 1 week; rewarm gently before using.