Pricey Sky, I agree it does depend on whoever is attacking to be a threat. No Sky has never chased attack after attack, because they've never been forced to.
Indian cyclist, there are many substitutes/omissions in there, Rodriguez for/with Moreno, quintana will surely be there, a number of guys from tour de suisse. Attack after attack come after you've dismantled the train. So it would be Froome and Porte grinding away to pull attacks back. Or if they choose not to respond to the initial train by another team, then you see Sky vs group of favourites, I'll concede Sky could win that anyway.
Escarabajo, In general I agree with you, that's why this approach is low percentage, however not as low as not trying anything and hoping for the best. When did anyone try one of these tactics against USPS? The closest I can remember was Vinokourov attacking...followed by Kloden bringing him back. I also remember T Mobile in 2005(?) using the train themselves, only for Armstrong to hang on and win himself. However they were trying on the ultimate climb, not before.
The idea is to "race" against sky, make them double guess their strategy, and perhaps slip up. Even let a lazy stage 15 break go with 20 riders, one of them 15 minutes down and give them 20 minutes. Whoops. Another strategy would be put a dangerous rider in every break, and try to make the breaks big enough to be dangerous from day one. Again I'll admit this is low percentage, but better than nothing. At best you end up with a victory, at worst 10th and boatloads of TV time. Most likely Froome still wins, and a GC rider going on the early attack finishes 2 positions lower than not trying.