Leverage (of a solution) is the degree to which it satisfies the following two criteria (which are, in general, conflicting): (a) number of problem situations to which it applies, and (b) extent to which it provides the complete solution needed for the specific problem situations to which it applies. Leverage is the product of these two criteria. (Hybertson 2009).
Hybertson, D. 2009. Model-Oriented Systems Engineering Science: A Unifying Framework for Traditional and Complex Systems. Auerbach/CRC Press, Boca Raton, FL.
Leverage describes the balance in system thinking between making specialised system to solve a single problem well vs making generalist system which can be applied to a wide range of problems (see Principles of Systems Thinking).