Portrayal is important. Because Shodaime was said to be the only one to beat Madara on several occasions.
No it's not in the battledome, only in the manga. It's as if i was saying Jiraya is stronger than Itachi because the manga said so, but i'm pretty sure you disagree with the statement. But since you really want to involve portrayal into this, care to show me the mangapage where it's said only Shodaime could beat Madara? They've been portrayed equal sure, but their equal portrayal was made without comparison to others beside Sasuke or Naruto in terms of potential. Furthermore when said manga portrayal happened, it was either when Minato wasn't partner with Kyubi(so no BM), or when he already lost an arm, so infact the full power of BM Minato(with both arms) was restricted in this manga. From this point, the hype and portrayal you mention may not even count him in
With the PS, Mokuton and Rinnegan, Madara will devastate the surroundings to such an extent, that FTG Kunai will mean nothing. Having all powers Nagato had means Shinra Tensei which blows up a village, further he has multiple meteorites, the perfect Susanoo which can bust mountain ranges and Mokuton, which can cover the entry battlefield. As an Edo, without any drain of Chakra.
No FTG kunai play a great role here because the teleportation speed of FTG is untraceable. Because of this, with markings around the area, deflective destructive moves like Bijuudamas could be dangerous because Madara couldn't even get the time to guard himself in time, not knowing the direction of said moves. The kunais are also tiny. No matter how much Madara would be destroying the battlefield, he would never be able to destroy all those tiny marks around the field. It's basically as if you were saying Madara could destroy every tiny bit of sand around a battlefield made of sand, and Minato's kunai spreading range exceeds that of PS by far, which could help him to dodge any dangerous attacks at a needed/given time
The Shinra tensei is an invisible force. Creating it would make the Bijuudama detonate. It's basically like an invisible barrier. The impact between both attacks would make the Bijuudama explode. It's for that reason Deva used Bansho tenin instead to counter the attack
Preta path only absorb incoming attacks. It would never absorb an explosive blast from a Bijuudama. Furthermore, it would rather be a mistake since he would be absorbing Minato's chakra, and FTG can teleport anything connected to his chakra
