So I have a potential customer with an interest in bioweapons. This sort of thing is important, because Mad Science requires all sorts of expensive supplies and equipment (and that's not even counting the secret lair, the pay and benefits for my minions, the emergency escape arrangements, or the kids' college funds).
Now, this customer is interested in taking over... some nearby territory, let's say. To do that, he wants something that will drive people away, but doesn't look like a genocidal assault initiated by his gov- er, by him.
So, after a bit of haggling, we reached an agreement. I will provide a small, fast-breeding predator that will rapidly overrun the area he desires, and a custom-tailored virus which will kill them off after they've done their job. The virus, by the way, is 98% guaranteed not to get into the local ecosystem and cause grotesque and violent mutations. (He could have gotten the 100% guarantee, if he'd been willing to shell out the extra five hundred thousand.)
So, after considering numerous ideas, I've settled on a design for the predators: they will be vampire porcubats. That's right, I'm creating an unholy hybrid of porcupines and vampire bats. To keep things interesting, and to keep my skills from atrophying, I'm developing my crossbreeds the old fashioned way.
This is harder than I remember it being - and far more difficult than designing a porcubat embryo from scratch would have been. Still, the extra challenge keeps the wits sharp... and while this method may be time-consuming and obsolete, it's so much more satisfying than the modern technique.
The real trick is to get the bats drunk enough to think this is a good idea.