I'd have welcomed alternative uses - so far, it's pretty straightforward.
> Blood beasts, in making all blood as one, could serve as universal transfusions!
> They could be distilled into healing agents!
> A colossal blood beast, stuck in a magical trap, could leak and feed a debased tribe with a fountain of unholy blood!
It looks like a good sub so far, although personally I would ditch the entire "Immunities" section, (A bit too stat blockish, like you'd find in a D&D monster manual for my taste) and work the info into some type of anecdotal presentation to make it more fun for the reader and less dry.
"Renthwrith and me thought we could take out a blood beast easy as skinning a drowned rat. I hit it with some charming magic to make it hold still and Renwrith pumps it full of poison darts.
Unfortunately the damned thing seemed to ignore my spell and his darts didn't do much more then draw it attention; away from me back towards him. What'd I do? I cut my losses and ran for it! Last I seen, Renwrith was trying to fill it full of arrows as it charged his hidey hole in the rocks. Haven't seen him since..."
It seems to me that with these creatures being so powerful, so difficult to kill, and so easy to multiply, that they would quickly overrun an area. That would definitely be a good plot hook on its own. The players could be given clues as to the wizard who created them and then try to find something in his notes to help destroy the blood beast infestation.
This not just an excellent GM's tool but an excellent players tool as well. This amplify the traits of the character, as IF-J says some players have different instincts. This forces both the player and the GM to wonder what the character is thinking and then amplify the results. I wish you had written this years ago.