Ryan, I was thinking about this while at work and realized that what I think of as a typical service is not how everyone does it.
I have never seen an all in one setup in this area, and an outside disconnect for a dwelling unit is very rare.
Here is note 3 from 250.66
3. Where there are no service-entrance conductors, the grounding electrode conductor size shall be determined by the equivalent size of the largest service-entrance conductor required for the load to be served.
It sounds like even if they install a 200 amp panel that they could size the GEC by the calculated load.
In the absence of load calculations maybe just have them size it to a 200 amp conductor?
Glad to help out, sorry if I came across to strong.
Take Care, Bob