21D20N Suggested Itinerary Question

Looking at doing my first foray into Japan (Early 30s, male, travelling with a friend) and have about 22 days (fly in on the 9th of June, fly out 30th of June) to do whatever. The suggested Itinerary is an attractive option as it gives me a solid framework to build on.

1. Is the suggested itinerary on this site (http://www.japan-guide.com/e/e2400_tokyo_19.html) a viable option? If so, how much tweaking should be done to what's suggested there?

2. I notice a few cities have suggested day trips. For example, with Tokyo (which the itinerary suggests I stay there for 4 full days, plus day I fly in) I have the option of doing a side trip to Kamakura and Nikko (one day each) as well as 2 full day schedules (Western Toyko and Asakusa/Odaiba). How sane/viable is it to spend my 4 full days in Tokyo doing all 4 of these things?

3. Same as question 2 but Kyoto (4 full days) which suggests a side trip to Nara as well as 2 full days (Eastern Kyoto and Arashiyama) and a half day (Northern Kyoto)

4. Has anybody done it? Are there trip reports or what have you from users who've done this itinerary that I can read/leverage from?

Hope these questions aren't too stupid!

This is a great itinerary.
I assume a 21 day JR Pass, which you can use for your trips to Nikko and Kamakura, as well as around Tokyo on the Yamanote and Chuo lines, and activate it so it is valid for your last day back to Narita.
I also assume you are flying in and out of Narita: arriving early AM in Narita, and flying out from Narita in the evening (QF flights)
Some tweaks could be:
1. Go directly from Tokyo to Kanazawa, early in the day, by the new Hokuriku Shinkansen: this will give you a full day in Kanazawa on arrival, and spend 2 nights there
2. Kanazawa early morning to Shirakawago (Nohi Bus) then on to Takayama in the afternoon
3. Morning in Takayama then on to Nagoya for 2 nights: with Ise Shrines for day trip.
4. Consolidate all the time in either Kyoto or Osaka (we usually stay in Osaka, for 7 nights: : its cheaper, more food options, and we have family there, and do loads of day trips):
5. once decided on which city: do day trips from there: ie Osaka from Kyoto or vice versa, Nara, and include Himeji as a day trip as well.
6. Send luggage on from Kyoto/Osaka to Hiroshima/Miyajima
7. Go to Mt Koya early in next day, with overnight stuff in a day pack, spend day there, and overnight,
8. next day Hiroshima/Miyajima, with an overnight
then onto Nagasaki.
9. Consider breaking the return trip from Nagasaki to Tokyo with a night in Okayama: half day to Kurashiki, or explore Korakuen
10. Okayama, to Narita, with a change from the Shinkansen at Shinagawa: much easier transfer than in Tokyo station.

Just my thoughts.