But if you want to we can open up the hybrid can of worms... I'll try to give you some info without taking sides
Many colubrids can interbreed with other species. Not all combinations have ever been tried. There is no master list. You will be more successful breeding species that are more closely related. There are many issues. Many speceies will ignore each other. Some individuals are more or less picky then others. Kings may try to eat foreign mates. Different genes may be incompatible resulting in slugs, deformities, unfertilized eggs, or females mate and never become gravid. The offspring of hybrid colubrids have frequently proven to be fertile but sometimes are sterile.
By "strengthening the bloodlines" I assume you mean something like hybrid vigor as is found with mutt dogs. This is not really the case with snakes. All dogs are the same species. They have been line bred for literally thousands of generations. Along with desirable traits, weaknesses are often propagated. By breeding two dif breeds you mix up the gene pool (within the same species) and possible get a healthier offspring.
Snakes have not been bred for that long. Most captive bloodlines are from wild stock within the past few generations. Maybe some of the oldest bloodlines are near 40 captive generations (probobly with some wild stock mixed in though). Even with all of todays selective breeding no where near the damage done with dogs has been done to snakes. I would think you are more likely to cause deformities or problems DUE TO the hybridization then you are to develope stronger offspring.
The first artificial insemination that resulted in live affspring was just carried out by some vets at a zoo with eastern indigos. As of now this is not a viable way to produce snakes for the private keeper. It may or may not ever be.
Buy a book. Buy two books. Your kings probobly won't eat each other.
