[samurai007]

I didn't know you have a JR Rail pass... that would cut the time to get to Hiroshima considerably (down to an hour, maybe a little less). But I still think Himeji/Hiroshima/Miyajima in 1 day is pushing it a bit. If you really flew through everything, you might be able to do it, but you probably wouldn't fully enjoy it in such a hurry. But with the Rail pass, it could conceivably be done, especially if you start early in the morning, leave Himeji by around noon, don't stop for any sights in Hiroshima and just go straight to the Miyajima ferry.

Day 4 you should be able to fit in Koya-san, I would think. Here's how I'd do it (assuming you haven't already booked hotels).

Day 4: Day trip to Koya-san, come back to spend night in Osaka.
Day 5: Day trip to Nara (Nara is closer to Osaka than it is to Kyoto, so leaving from Osaka will save you some time), and travel to Kyoto to spend the night there.
Day 6: Temples in Kyoto, as you planned.

Also, you have 5 days planned in Tokyo, which IMO may be a bit much (but I am biased against the big city, and much more attracted to the countryside, as you know). I think rather than squeezing some of the other places down to a half day, you may want to consider giving up 1 of the 5 days in Tokyo so you have more time elsewhere.

You can get burned out on temples, but the key is to not see each and every temple, but the ones that really have something spectacular and different. Places like the Daibutsu-den in Nara and Okunoin in Koya-san are not your run of the mill temple, but something truly unique and memorable.