Of those options, I went with a Starfleet Academy series. Has the most potential for character growth and development, without relying on catsuits, big space battles, or hostile aliens every single week. Also it could give the chance for some cameos from TNG/DS9/VOY characters.
Out of the others: A Klingon series would be dull; Mirror Universe would mean that the focus would be on the baddies and the horrific things they would do to get ahead; and 25th century would run the risk of being very technobabbly.
Commander Austin Harris, First Officer, Deep Space Nine (by FltCpt. Bossco)
8.01 - Darkest Before Dawn
(Chapter 8 added, 12/09/2015)