Do you think officers should have MOS-specific degrees (e.g. Aviation, Ordnance)? What are your thoughts?

No. Keep in mind the Commission is as an Officer. Not as an MOS Specific Officer. Just because someone starts out in Armor doesn't mean they will stay there. Additionally, because of the way selection works (people don't always get their first choice), it becomes significantly more difficult to make assignments if you make the requirements more stringent than absolutely necessary.

Some fields should have specific degrees like Law or Medicine (which they do), while others will acquire advanced degrees and PME over the course of their careers.

For my more serious, non commissioned, non non-commissioned officer opinion no I do not think so. Officers aren't supposed to be technical experts so I believe such a requirement misses the point of what they do. They're leaders, organizers, planners etc.

Requiring related civilian education would severely limit where you can place these officers as you can only put them in capacities related to what they studied in college.

Kind of hard to major in Armor, Infantry, Cavalry, etc. So no, I do not. College shows that they are educated and are able to learn more. The military will train them in what is necessary.... But I would recommend majoring in something in your field (Mine would be CS or Informatics).