Spectator mode is a good idea, but as others have said, there are tons of youtube vids out there with commentary. I can see the jibes about: "go watch a vid! or go spectate ___ FC/LS"
That being said, I wouldn't mind having it implemented in PvP (if it ever becomes more exciting to watch..)

Learning/God Mode: They already have Story Mode, Hard Mode, and Extreme for primals. While not quite the same thing, you still get a feel for the fight. They just tweak and add actions. PUGs are really where it's at for learning and you do see them in PF. PUGs+vids+forum discussion (that is what forums are for, right? strat discussion and suggestion??? anyone?) should be sufficient.
Of course, this mode is entirely appropriate in music/rhythm games :P