Oden fan or not this would be bad writing from Oda, I don't why you and some others can even defend this horrible writing if Oden is actually alive. For what because you want to see Oden fight Kaido again and see him interact with Luffy, I'm sorry but that's not a great reason for wanting Oden to come back to life.
Their are multiple reason why a comeback would make sense, not him but at most Toki.
We don´t know anything so far about Toki, for sure she had one of the brokest df, her death would mean her df would get gone, if such a op df would come into the hands of the WG it would mean bad things for the country where Toki come. Im sure she had plans, she didn´t get much screentime in Oden flashback. The alliance need right now help, alone with Tama and some fodder joining Chopper doesn´t change the situation above. I rather have a Oden helping at the rooftop then to get a fucking Olin back, no one need that too.
In case Oden and Toki could have many reasons to beeing back, even though is would be a shorttime.
I see many mangas who could handle a future travel ability, if Oda can explain it good enough, why it would be bad?
Toki die without we getting more focus on her, Oden die to sacrifice himself to save the Scabbards.
It would ruin Oden's backstory
Why?
It would ruin the whole point of the Scabbards
How, the Scabbards do in the end what Oden ask for them, they build up a very strong alliance, protect Momo and fighting for his sake, why it would ruin the whole point of the Scabbards?
It would ruin Momo's character growth
Momo growth on his own, Oda try to make it clear that Momo is a different person, he has his own character, during his growth alongside Kinemon, he do it on his own. Oden comeback wouldn´t run anything about Momo character.
It would ruin the whole point of Yamato trying to carry on Oden's will
And she will do it after Wano again.
My whole theory is based on Oden going back in the past(timelimit of Toki power?) after Kaido is defeated, in that case the character building of the Scabbards,Momo and Yamato would still stay, if not would even increase.