This is really a very fun game, I love every bit of it and the unique mechanics and game physics kept me engaged. I have only played the online version, so the following suggestions may have already been implemented. My suggestions:
1. If you change the patient into a monster, you should earn less money, almost like a tip if they live (I get to leave alive, here is more money type deal). This balances the gameplay to not just turn everyone into monsters (I tried this on day 6 and just made everyone monsters, which got a lot of cash in and a lot of new customers).
2. Linked to the above, have a potential balance and game over if there are too many monsters released, almost as if they turn on you because of being the majority.
3. Potential hard mode where mechanics remain the same, but the patient is on a timer. If you don't heal them in time, they die and you have to pay a fine.
These are merely suggestions from someone who has never made a game, bit enjoyed every bit of yours! Keep up the great work!