I don't believe there is such a middle ground, actually. I'm not a huge fan of Bayesian logic but I think it's suitable here. There's only three possibilities:
You are the world's policeman.
Somebody else is.
Nobody is.
Nobody being the world's policeman will lead to whoever can filling the gap and taking that power, quite possibly after a bloody war with other would-be policemen for the position. China's trying to establish their dominance over the South China Sea right now but if they could instead dominate and regulate trade across all the oceans of the world do you think they wouldn't? Of course they would.
Being the world's policeman puts you in an inherently superior position. Regardless of good intentions, you have a certain amount of advantage and in things like negotiations you're going to come out ahead compared to nations that rely on you for protection. There's no way around that and it's a perk of the job.
Now it's possible the cost of being the policeman is higher than it's benefits. The US is in a weird position that due to constantly swapping leadership, it can rarely stay aimed at a single target more than 8 years before tearing whatever it built down out of spite for the previous ruler. Another country that was more willing to squeeze and that had a more stable government could abuse policeman status far more. But it wouldn't be to the US's benefit to let somebody else, and by that I mean China because they're the main contender, control world trade.
Till 1945 there were no such thing like world policeman.Not even Europe policeman - becouse England from 18th century was making coalition to defeat any country which try that.
And you knew - world not ended.In many regards,people -even occupied - lived better then after 1945.
So,why not come back to that natural state ?