Let's face it: Miaka is well-meaning and has the ability to decimate Nakago's supplies by eating the food meant for his armies, but there are other candidates who would have made more effective Suzaku no Mikos. Since Suzaku, like the other gods, has a habit of stealing a priestess from another world, why not another anime world?
5. Miki from Marmalade Boy. Roughly the same emotional maturity to start with (i.e. almost none), ability to create angst over trivial situations, and tendency to fall into melodramatic, contrived crises. Oh, wait -- we wouldn't be able to tell the difference.
4. Hitomi from Escaflowne. After all, having already been abducted from her home and thrust into a turbulent fantasy realm, Hitomi has all the ropes down. Her talent for fortunetelling would surely help the Suzaku seishi in intelligence-gathering, which they're not particularly good at, and her stubbornness would be a welcome factor in the fight against Nakago & co. Van and Allen might be upset, though.
3. Miyazawa Yukino from Kareshi Kanojo no Jijou. Like Miaka, Yukino is a schoolgirl, if that's what Suzaku wants. Unlike Miaka, she's athletic (A in P.E.) and smart (highly-ranked in her school). Plus, her demonic rages would put Nakago to shame. Parting her from Arima would be cruel, though, so we'll have to look elsewhere.
2. Asuka from Neon Genesis Evangelion. Comes with Big Scary Red Eva. A girl used to dealing with Angels and Shinji would find no trouble dealing with the Seiryuu seishi or the Suzaku seishi's general wimpiness. In fact, she'd make them shape up right quick. Of course, with her temper, she might end up trashing both Konan and Kutou with Unit 02.
1. Hongo Yui from Fushigi Yuugi. She's also a schoolgirl, she has smarts, and she's also in love with Tamahome (if that romance matters to you). Her determination and ability to survive a bewildering situation, not to mention psychological abuse and manipulation, are better than average. Waitasec -- she's on the other side.
Do you know, I almost find it in me to pity Suzaku.