I think this is right, but I also think Michigan is as good or better of a fit.
For IR in particular, I think this Foreign Policy survey-based ranking of undergrad (and Masters) programs is really the best resource for getting an idea of how IR professionals see these programs:
For undergrad programs, Michigan was ranked #14, Middlebury #28. Those are both quite good, but again if anything Michigan is a bit better regarded.
I note for IR Masters programs, Michigan was tied for #18, Middlebury (Monterey) #33. Both again good, but this sort of thing is why I am concerned about placing too much weight on the possibility of doing a Masters at Monterey, when there are so many other options.
I don’t have a similarly useful source for professional views on Environmental Science undergrad programs. But Michigan is in the Top 30 of the QS global rankings:
The QS rankings do not include LACs, but I still think this supports the thesis that an IR person with an interest in ES would rationally be very interested in Michigan as one possible choice.
But again, if someone actually preferred a small LAC in a rural location, Middlebury would be very competitive too. I would just be hesitant to conclude Middlebury would actually be a better academic fit than Michigan, given Michigan’s recognized strengths in both IR and ES.