Tenseigan takes up two eye spots.... Not full power I guess...
Besides wouldn't a tenseigan not be suited towards an uchiha's body... Or any random person's body I guess...
Like how rinnegan suits very little people... such as Uchiha/Uzimaka...
With Obito only being able to wield it cause Hashi cells...
That is if tenseigan is an hyguu thing and not an Otsutsuki thing...
Well the Rinnegan theoretically needs the power of the Sage (gained through combination of the younger and older son's chakra, harvested from their respective transmigrations). An Uzumaki can use it mainly because of their Kekkai Genkai (the whole big chakra, longevity and such) but as we have seen from Nagato it slowly drains your body of it's life force without the real requirements fulfilled. Obito could use it to some extent because of Hashimara's cells and his own Uchiha heritage.
For the Tenseigan, if one was able to achieve what is needed to sustain the Rinnegan without negative side effects, the body enhancement he/she would have gained through that should be able to keep up with the other ultimate doujutsu. After all this person would be "nearer" to the orignal source of all chakra (Kaguya/the God Tree) so I don't see why the body should have problems with the Tenseigan then.
For the thing if the Tenseigan needs two eye sockets, well you could always go the Kaguya way and get a forehead Rinnegan.