Dunno about the politics of grant funding so I certainly defer, but frankly I don't see why beginning pathology training, much less finishing it, with or without board certification, has any bearing on whether a given grant proposal is worthwhile. Sure, some research is geared towards needing a qualified pathologist on board, and some has nothing to do with pathology. Depends on what you want to do. Plenty of people call themselves "pathologists" and do research in "pathology" without having an MD, much less without being board certified in AP &/or CP -- you probably met a few in medical school. This is all in comparison to getting a PhD -- probably no more useful as a degree in the simplest sense, but in reality most people think it means you have research cred and those interested -purely- in research I think should consider that over something like an MD.
As far as loans go, that depends on your personal financial situation. If all you want to do is "research" and have no interest in clinical practice, well, do that...but realize that most people will probably make more money in clinical practice, and for those paying attention it never really looks good to drop out of training/residency. (For those of you who know going in that -all- you want to do is research, why spend the time and money on an MD you're not interested in and might not be able to afford?)