So I've been pondering this thread in my head as I've worked today and I remembered something. In Dr. Strange there was reference to the staff of the Living Tribunal. The Living Tribunal (being) is the only thing, in the comics, more powerful than the Infinity Gauntlet.
And the Living Tribunal had a big part to play in the Infinity War comics. In fact, he was the one who deemed that Adam Warlock was too unstable to wield the gauntlet and that the six infinity gems must never be used in conjunction ever again.
The Living Tribunal exists in the multiverse, he has no counterpart in any other of the realities. So, what does this tell us....
a) Via Dr. Strange we know that the Living Tribunal exists in the MCU.
b) In the comics, the Living Tribunal's word is that of God in the Marvel universe, even the cosmic entities have to abide by his judgement.
c) Being more powerful than the gauntlet, he'll probably be used, and that Easter Egg was probably put in Dr. Strange for that reason. If he is in the film (or the next one), than the multiverse will definitely be the key to defeating Thanos.
c) Thanos thinks he's restoring the 'balance of the universe' but that is the Living Tribunal's exact job description. That's precisely what he does, he is an impartial judge. He acts in the greater interest of the universe. In the comics the Living Tribunal let the events of Infinity Gauntlet play out, and didn't intervene until Infinity War when Warlock got the gauntlet, but since they're kind of giving Thanos different motivations in the MCU, it's possible the Tribunal's judgement will be different.
d) Let Thanos take the time stone. Strange has the answer to stopping Thanos right under his nose. All he needs to do is to summon the Living Tribunal. If he could figure out that it is even an option in the first place.
e) Sadly, though this breaks my heart, Adam Warlock will not be in Avengers 3 and 4, which makes me wonder if they're going to have someone else take some of the plot pieces he played in all this. For example: the person who gets the gauntlet after Thanos... it would have to be someone all the heroes trusted not to be seduced by the power of the gauntlet, in Jonathan Hickman's Infinity series it was Cap who everyone voted to wield the gauntlet. But whether they decide on Cap, or Tony, or Strange, or Thor for this role, ultimately the Living Tribunal will intervene and order the stones separated by caretakes if they follow this thread, each caretaker getting a stone that they cannot use in conjunction with the others. Who then will those caretakers be?
We may already have an answer to that last question...
Also, bringing the Living Tribunal into the MCU fits into Feige's promise of a more cosmic Marvel going forward.