I'm going to take an independent post to clarify my thoughts on armistice. I think any reasonable person would agree this is a reasonable outcome given the circumstances.
Britain naturally has had a very advantageous position that makes invasion difficult. It's been invaded by the Romans, Anglo-Saxons, Danes, Normans, and if you count William in what was more a political revolution, 6 times in the past 2000 years. The invasion of American men of English women twice last century is a separate case.
I believe Britain has very favorable circumstances to seek a separate peace, come off somewhat close to the status quo. To do so it has to screw over France.
The Germans aren't in any position to invade, or in any position to demand the Royal Navy. Neither is the US.
If the United States is to go to war with the Allies, and Britain faces the extreme challenges and adversities it would, I think it screws over France, gives back the German colonies, keeps its navy, and withdraws its army back to Britain. Given Wilson's "peace without victory" mantra he maintained prior to and after entry into the war, the US may make limited demands based on popular and congressional demand (Wilson went to war on such demand).
France has a hell of a reckoning ahead of it. It's going to have to surrender if the British make a separate peace. If Britain undertakes the strategy you've laid out and doesn't succeed - it's going to have a hell of a reckoning ahead of it.
I think this is the most worthwhile option Britain has.