Why not just have Kaguya as a pre-requisite instead of Hachimon and nip it in the bud? you can't have hachimon and Kaguya in the reset system together. It can still be a rule that you can't use eight gates with this, but as far as the reset system goes, there's simpler way to go about this.
Sage Mode is being noted as a requirement to get Tenseigan >>
What? Where in the world are you getting this from?
Or do you mean that the sage resets (Rinnegan/Sage Mode) should be used for it? Because that's already a given...
Um, considering the manipulation of natural energy is required to form any sort of sage chakra (even Six Paths Sage chakra) I think mastering sage mode is kind of a must for this dojutsu. There is no logical reason to use the Rinnegan resets unless you want people using full Tensaigan at reset 1 instead of at reset 6, and we still don't even know what "full" is since they haven't dubbed or subtitled the thing yet.
And as far as the "alternative for Hyugans to go", I argue that the only option for Uchiha (to an extent) is to go Rinnegan, unless they want a sage mode enhanced mangekyou sharingan (which is not common from what I've seen, but possible I suppose). For all practical reasons, why would Hyugas go anything but sage mode if they had to go down that tree? A sage mode enhanced Hyugan with a biju cloak is practically a Hyugan enhanced with Tensaigan as has so far been postulated for use here.
Had a feeling the combo was why the seal looks different.
Also no kg buffs rinne whatsoever? Lol, need I remind you of the gate + raiton no yoroi human path drive-by trick.
If the chakra cloaks from the byakugan, two eyes to use it is obvious since it takes two to bring any dojutsus real power out. Sharingan doesn't get susanoo without two either.
As for making balls and other shapes from chakra, that'd be easy with it.
If I may ask Warren, how many people actually do that? I am not saying it is possible, but realistically speaking, someone who abuses that frequently is not going to be someone people are going to zone with very often if at all unless they either want to prove a point or have a way to counter it.
I am not saying let's start buffing Rinnegan too now, but that trick is incredible cheap, and is almost worth a voiding really for how OP it can be. Tricks like that, idealistically, do not stay in circulation for very long.