People get way too attached to named lines. Once the original breeder of that line stops having input on the breeder selection and culling it really isn't truly that line anymore. Chickens aren't pedigreed, best advice for the breed would be either outcross as suggested, or ditch the inferior "line" entirely and continue breeding your other line that is more in line with what you want.
I understand this and agree with the idea of a breeder's line stopping when it leaves their hands.
However for most serious Java breeders, it is not about being enamored with a particular breeder's strain as a means to sell birds or claim any quality by continuing to use their names. It is about tracing pure bloodlines back into history because there have been so few of them for the past 100 years. One Java breeder has been keeping records and disseminated charts so we can see where things are at. There are a lot more historical aspects at play with Javas than what most people deal with in their breeds. The purity of Java bloodlines has been a topic of concern for many years and utilizing the oldest names of the strains help to more easily ID who has what birds and how they are doing.