If you're going for industrial-sized quantities, perhaps an industrial-sized tool can help. Could something like a butcher's band-saw be used to portion the frozen block directly?

How exactly do you even plan to cook a 50 lb piece of meat? I mean they're your tastebuds...if you want to ruin the meat, by all means cook it, freeze it, thaw it out and eat it. As for the science, I suppose there is a small chance you could contaminate the meat with Clostridium spores and then get them growing again once you reheat the meat. It isn't any sort of large probability (well, I don't know about your cooking conditions--if you're cooking a big hunk of meat outdoors, yeah, you're going to get spores). It is mostly just that it is going to taste gross (and thus you're ruining a good piece of meat, a crime in my book, and disrespectful to the animal, but whatever) and why cook in 50 lb batches unless you're cooking for an institution? Just find someone who sells meat in reasonable portions, keep it frozen, and then cook as needed. You're just throwing it back in the freezer anyway. Cook 5 lbs batches for the week or something reasonable like that. Throw it in the fridge (and yeah, you can contaminate that too, but again, small probability). Besides, reheating stuff from the fridge is way easier and faster than reheating frozen stuff.

it would be ok to thaw very briefly (you don't have to completely thaw to do this), re-portion into smaller portions and then refreeze still raw. do not thaw, cook and then refreeze.

if im understanding you correctly, you want to thaw, then cook, then refreeze? thats not a great idea. it does f*ck up the meat, and its not safe to refreeze things. once food is thawed, it should be consumed. when i buy a large quantity of meat, its normally packaged how i want it (vacuum sealed) in one pound portions, or in individual cuts and i thaw them as needed.

if im not understanding you and youre asking if you should freeze it raw, or freeze it cooked, then you want to freeze it raw. depending on where you are getting it from, it might be flash frozen and wrapped for you.

Keeping it frozen while raw would be better for quality than freezing it cooked. While raw, the meat fibers hold more moisture and are less susceptible to ice crystal damage. Since cooking the meat would remove that moisture, freezing after cooking would ruin the texture and, depending on the cut, make the meat very dry or very spongy. You are better off buying some good butcher paper and carefully portioning out the frozen meat and thawing it when you're ready to cook.