The available information would suggest that the variable called military tradition is used to pay for generals; and that once you buy a general, you lose military tradition. I might be wrong in this assumption, but wouldn't it be better to have a requirement of military/naval tradition, i.e. you need to have x tradition to hire leader y, and x depends on how good y is; but you pay the generals with money (an initial sum + monthly or yearly installments), as they, too, need to eat and want diverse luxuries. The diffrence would be that tradition is not lowered by the hiring of a general.