I honestly think you're making a D-rank jutsu way more complicated than it has to be. I've just shown you their chakra is strong too. Kisame, someone who's known to be the Tailless Bijuu couldn't replicate what Hashirama/Tobirama did, because he has high chakra reserves, not strong chakra. The stuff about Senju and Uchiha is irrelevant, considering you can work on both Yin & Yang energies and overall, produce a stronger chakra. It's like saying Senju fodder have the same amount of Yin energies as Hashirama.
Viz have always translated Shunshin as teleportation. They translate Hiraishin as Flying Raijin. FTG speed does not vary whatsoever, Tobirama was referring to the delay
before each usage of Hiraishin. You can clearly see that there's delay before Tobirama's Shadow Clone can use Hiraishin [
You must be registered for see links
], whereas there's no delay when Tobirama taps Obito and teleports him out [
You must be registered for see links
]. Also, do you see Hiraishin being slow when Tobirama's Shadow Clone used it?
Shunshin requires very basic use of chakra control, has little to do with chakra strength, and is more to do with physical speed.
GL put it perfectly imo.
Last post regarding Shunshin, caterpillar's right, this thread's going off topic.