The theory that works and still could hold is that Odin was a similiar Stone seeker.
He at one point had Time (On Earth), Reality (In Bor's hidey hole), Space (On Earth) as documented already.
It would also explain (if they don't go Odin force with Thor's source of power) his kids/people he trusts the most having very unique powers even for Asgard.
Further, why the dwarves could forge a gauntlet as well as Thor's Stormbringer. They already were working on it. The gauntlet in his throne room the "model.”
The only gap is how did he get the soul stone, but to that I think, what if he's the one who put it there? The soul for a soul step was very much in line with his Mjolnir enchantment.
I doubt they'll go this path, but Odin being the reason the stones are so easily found AND the soul stone being in his possession being the reason he diverted from Hela would be near perfect.
The only stones that may or may not have been in his grasp was the mind stone (Thanos got it from somewhere) and the power stone (which was outside the 9 realms, but again, maybe after Odin razed the planet, he set it there).
I always heard a version of this theory that Odin successfully collected all but the Soul Stone (with Hela assisting him) but when he found out what he'd need to do to get it (sacrifice his daughter) he gave up on the whole thing. He didn't tell Hela what was required for it, so all she saw was her father giving up on what they'd fought so hard to accomplish.
This is what led to their falling out, and him banishing her. After her banishment he stashed the rest of the stones, and did what he could to prevent others from attempting to gain them all.