If Obito revived madara using Rinne rebirth without reanimating Madara would he still be young and if Madara was reseurected old then how would they succeed in project Tsukenome ?

i think Madara & Zetsu didn’t know there was a “hack” through Edo Tensei that could allow Rinne Rebirth to revive Madara to his prime

if they could’ve, the plan would’ve been to immediately revive Madara with a young body *as soon as possible* after his old body’s death; they could easily use Black Zetsu on Nagato or some other pawn

and this also makes sense if we concede that Kabuto is the one who perfected Edo Tensei (invented by Tobirama, developed by Orochimaru, but taken to another level by Kabuto)

so Madara & Zetsu could not have known how they could have used Rinne Rebirth with Edo Tensei because Kabuto’s Edo Tensei had not even existed yet; hence they could not have planned to revive Madara in his prime, and had to rely on a faux/second Madara (Obito)

i think this is why, when they met in the war, Madara said to Obito “you were supposed to determine the *appropriate time* and bring me back with Rinne Rebirth”

here i think he’s referring to a time when all the bijū have been successfully captured; then all old Madara has to do is get more life force from the Gedō Statue and have enough strength to become the Jūbi Jinchūriki (and cast the Infinite Tsukuyomi)

i’m pretty sure other fans have this theory too, i myself pieced it together from reading multiple people’s headcanons lol (since we all know Shippūden is riddled with plot holes…)