1) The match would never last a day.LoL, you're saying that he'd block Kaido for a day or what ? Hybrid would blitz him like he did to current Luffy. Oden was a legend, but he was a legend against inexperienced, young Kaido. The guy had Moria as a peer back then. Years later even WB avoided him.
Kaido has improved a lot since then. We see lightning haki, another form of his fruit + lots of experience accumulated. You're dellusional when you say he hasn't improved when it's been stated in the manga that he has.
He has just shown haki of the exact form they had.
I'm not making shit up. LoL, let's stop here with the Oden can Blitz Hybrid Kaido.
I'd lean Shanks & Mihawk because I feel like their fighting styles are more conducive to team fighting. A Hakai from Shanks & Mihawk would likely be superior to BM & Kaido because they are both raw swordsmen & haki masters vs. BM & Kaido who are more well rounded with DF abilities and monstrous durability.
In terms of feats, BM and Kaido take it because those 2 have serious stuff while the bladed duo don't have much feats.
But with the combination of the narrative and statements and future plot progression, it makes more sense it's Shanks and Mihawk.
Extremely close fight, but Shanks and Mihawk take it.