I'd have a hard time buying "Day of the Dove" with Kor; as awesome as his character is, he's a very different man than Kang was. First off, it would be strange to see Kor commanding a ship of his own. In "Errand of Mercy," Kor came across as more of a bureaucrat, someone who has goverened countless subjugated planets across the Empire - Organia just being another routine occupation for him. He almost seemed tired and bored with the routine, being relaxed and casual about the rules applied to him, so much as being able to smile about them (the issue of his office being wiretapped being one such example) all while having a hard-edged and strict devotion to them.
Kang was more of a Klingon version of Kirk; he was much more serious than Kor, and a different brand of "scary" (different, but equal). He had close bonds with his crew (hell, his wife was the science officer) and was concerned with their safety the way Kirk was concerned with his. Kor seemed more like the kind of guy who is used to having many people under his command, but also used to those people being different every week. While Kang commanded a smaller group of people with tighter associations, Kor commanded entire planets, with an understandably looser association with the millions under him.
I could go on and on but I don't want to bore anybody, PLUS I'm sure I'm preaching to the TOS choir, as it were! Bottom-line, I'd have a hard time seeing the "planetary governor" Kor as a battle cruiser commander.