Or Fox river socks.
Seriously you are WAY over thinking things. If you have prior issues with blisters that is understandable. I think I lost half of my heel from one day when we ran through some wet in tennis shoes and didn't get a chance to change for a whole day.
Here's the deal though, they will give you the boots you need, they will give you a chance to buy insoles (or bring custom ones) and you will alternate boots and tennis shoes for a week or so. Also you don't do any "real" running in boots, a few miserable laps around the gym but nothing measured in miles.
If all of that fails and you still get blisters, you go to medical. They will give you fancy creams, mole skin and a chit to wear tennis shoes until your feet get better.
Trust me, I know what you are trying to do, control what you can before you go, but believe me OCS is awful in some pretty creative ways. You can't prepare for it like this. Either that, or you have some jacked up feet and you'll just be spending some time at medical getting it sorted.