I think it´s a mistake. I think it is a good way to end up getting robbed, assaulted or a mixture of the two. The way you are describing your poly-substance usage leads me to believe you likely cannot exercise the immense discipline required to prevent yourself from blacking out. You mention you like Cocaine, but do not like the anxiety it provokes, so you´re using Ketamine and Alcohol to overcome this anxiety.
I am also a drug addict. The way this tends to go is you escalate your intake of each drug haphazardly trying to attain that ¨perfect¨ place that you think exists. Like I said, this typically leads to taking too much, in this case, I feel you would likely take a lot of Cocaine knowing you have the means at hand to counteract the anxiety. You end up taking to much Cocaine. You then overshoot with Alcohol and Ketamine.
Alcohol and Ketamine have different pharmacology. They have different durations of action, they will also be less predictable in combination like this. Ketamine is a dissociative, it is well-known and established that it will separate your from your senses, i.e. your ability to defend yourself. Given the unpredictable nature of this combination, I highly suggest not attempting this in public until you have a better idea of how you will react.
TL;DR if you´re going to do this, do it at home, not out on the street. If you end up in a K-hole, then you won´t be in danger of being robbed/assaulted.