This sounds ethically questionable to me. I wouldn't rule it out entirely, but I'd want to see a well-reasoned argument, both technical and moral, that it was likely to lead to greatly reduced suffering for patients. Even then.... growing a body without a brain likely would not produce a model organism with predictive ability for human diseases.

I believe it could for a large number of tests. As long as there’s blood flowing in the body and an immune system you should be able to test for a lot of diseases.