This is sort of a multi-part question that adds up to one larger question:
- Can Sauron get to the Undying Lands? (another question seems to have produced the answer to this - "No")
- Is the One Ring still dangerous even if Sauron can't possibly get to it?
- Is Elrond strong enough to resist the Ring?
- Could the Ring be taken to the Undying Lands, perhaps by Frodo, Bilbo, or Elrond?
Assuming the answers to these questions are 1. no, 2. not really, 3. yes, and 4. yes, then wouldn't it be feasible for someone to just bring the Ring to the Undying Lands and give/send it to someone who could safely hold on to it? Say, perhaps, Eru Iluvatar, Manwe, Elbereth, Cirdan, etc? This wouldn't require the person in question to actively intercede in worldly affairs - they would merely have to accept a gift and keep it forever. Since humans (and/or elves and/or hobbits or whoever took the initiative in getting the Ring there, it would be more or less the same as bringing it to Mordor and destroying it, but less suffering and loss of life would be required in the process.
So basically, the overall question is: Why not send the Ring to the Undying Lands?
*Note - since sea monsters never seem to attack ships carrying Elves, Valar, or Maiar to the Undying Lands, despite Sauron's hatred of them, the sea monster issue is irrelevant. In any case, this question isn't about whether the ship would get there safely if passage were granted - it is about whether passage WOULD be granted and whether it would solve the problem.
*Note 2 - granted, this wouldn't get rid of Sauron, but Aragorn was free to set the terms of the Army of the Dead's deployment. If he said "You must serve for a thousand years" instead of "You have to fight one battle", then the Army of the Dead could have roamed through Middle-earth and Mordor killing off every Orc and goblin Sauron enlisted. Sauron would still exist, but he would be a more or less powerless eye stuck on top of a tower, with no hope of raising and army for a thousand years. If Aragorn said "You must serve forever", Sauron would be deprived of an army forever.