Actual Themistocle aura affects Ship class and multiply their BatchTimeModifier value for 0.5 while garrisoned.
After 30 or more units batch size, the aura effect is bigger than intended and thus unwanted because a player could garrison the hero in a ship, enqueue a batch of units, then ungarrison him and repeat the same operation over and over with different ships ( reported by temple ) .
This patch converts the aura from "garrison" type to "global" and uses Marine class to affect directly units template BuildTime entry in order to handle the otherwise exponential build time growth.