> Sick and evil.
Why? As mentioned, one of the chimera was a pig that had human blood. Pigs (or other critters) with effectively human organs would make marvelous hervestable sources of blood, organs, tissues, etc. Make a critter that does nothing but spit out human stem cells, and you'd really have something useful.
A mouse with a brain made from human brain cells would not have a human brain. It would still be packed within the mouses small skull, and would be mouse-dumb. It would, however, likely be suseptible to human brain disorders such as Alzheimers and the like, and thus treatments that work on a mouse would be directly transferable to humans.
After the blood and organs were harvested, you could harvest the bacon and chops too...
(Well, well, OBB...we meet again!)
Why not just clone everyone at birth? We can keep the clone in a controlled, perfect-nutrient environment (ever see the movie "The Matrix"?) and as we age or are injured, we can harvest replacement parts and tissue from our identical clone! We can start right now using identical twins.
If you aren't a believer in God, you wouldn't understand.
If you are a believer in God, then I'm surprised you don't already understand.