I am not sure I am 100% on board with what we are talking about but here is my take on it
You have 700 Kcmil of service conductor, that gets you a 2/0 grounding electrode conductor. in 250.66
Then you have a 600a service disconnect
That gets you a #1 EGC up to the point you have another breaker. I assume these are all taps.
Then you have a 75kva 3p 208 transformer with what looks like it will be a 200a breaker on the secondary. On the load side of that your EGC is #6.
The motor controller panel is protected at 400a, the load side of that will have a #3 EGC max or whatever you get from the individual circuit OCPs in 250.122. (again you didn't say but it is worth looking into)
The 5kva looks like you will just have a couple of 20a breakers and you will be running all #12 from that.
You are going to need a breaker or fuses from the Hoffman to get to the primary because you are >10x any conductor you would be likely to use.
I am willing to be wrong here but that is my first swing at it.
