I'd like to defeat the Jihad forces, drive them to unconditional surrender and make them as likely to threaten the US or the world in the year 2025 as the Germans or Japanese were in the year 1965, or as they are in the year 2007 for that matter.
Is that a bad proposition?
It will likely take way more than 10 divisions. 10 is a good start, though.
The increased size alone won't grant the military the national will to make them capable for what you're suggesting. We've decided on a modern system of warfighting that ties one hand behind the military's back. Now, making that hand twice as big will be nice, and it will help. We'll still be inefficient, but as we waste twice as much as before, we'll get twice accomplished.
It won't, however, change the fundamental military weakness that America's enemies cherish; our lack of will to get the job done. If 500 thousand Soldiers can't put an ounce of spine in a nation's back, 5 million couldn't, and that's what we need more than anything.