That explains alot and explains why raikage said he didn't even think minato could lose.
Your point about storing chakra in the kunai is also very plausible as that would give minato an infinite amount of prepared FTG without wasting an ounce of chakra. His potential for a long fight would be massive.
In essence, ftg0 seems like he travels through a rift/wormhole. He's sucked in at high speed and ejected out the other end at high speed, that's why they 'fly' when using it. And that's why tobirama was able to use a slash with a teleportation.
This puts a new spin on things, as if this is true, a lot of the counters in vs threads 'Stay out of his kunai reach/marking' are no longer viable. But the question is, how much chakra would something like that drain? It seems to drain a ton based on the size of the object, as he went from seeming fairly alright to completely exhausted after only teleporting the kyuubi.
This could also explain why a senju such as tobi wasn't able to defeat 20 ninja with the power of ftg, nor did he get a yellow flash moniker. The chakra consumption of the FTG-V0 is probably too great to effectively spam. It's possible that it could take even more chakra than a raikiri considering the person has to use enough energyy(chakra) to create that rift big enough for their body in the first place.
Guess the hokage will possibly reach the battlefield faster than we thought.
The difference between Flying Raijin and Kamui, is that the former does use seals.
your scan effectively proves you wrong and actually makes this thread more likely. Kakashi said
'...without weaving signs...'. That means he knew of the possibilities of S/t using hand signs. Probably that's another reason why FTG-V0 can't just be spammed herethere, and FTG-V1 was created. To alleviate the need for signs and to allow instant activation instead of wasting time.
Great Theory 
