To be quite honest, this is a fair trade-off. Sure, I relied on BP-Trainer to exploit and customize my fatty ASAP but at the same time 0.5.1's illness system demolishes the rate/pace of growth I usually go for with my fatties. I'm glad you have some control as to how the illness works and how you can stave it off completely if you know what you're doing instead of waiting X amount of minutes after giving the fatty a little too much food. What's worse is that once the fatty feels "better", they can get immediately get ill again if they eat something.
So overall, I'm looking forward to this update on Friday!