Such embryos are to be 99% human and 1% animal and so forth are potentially a great source for medical purposes. The embryos open every door that requires the use of stem cells. Body damages, neurodegeneration diseases, transplantation are just to name few.
Of course there is few considerations that need to be thought over, like the possible threats of transmission of animal viruses to humans. Over all there is the ethical discussion over the humanity of the created embryo and its use.
The article posted in Haabaa Infopool explains in easy way the merit and sense of the embryos all together with the possible applications and threats, please read it here: