This isn't just any guerilla war; it is a religious war, one that currently employs guerilla tactics in some places, terrorism in others, and full frontal assault where they think they can make it work... Hence, it is an all-out total war, at least on their part. To defeat them, means to defeat every single one of them to the depths of they tortured psyches. I do agree with you on one thing: do it for as little money as possible.
My solution: destroy the faith by ridicule of its supposedly invulnerable central icon, the Kaaba. Send a B2 from the central US, and carpet bomb it... with pigs. Dead pigs everywhere. Photograph the hell out of it. Then, amid all the screaming, wailing, and global outcry, give them 24 hours notice to get out of town. Make it really clear. Then level Mecca, completely, not a single standing stone. Show them what power means.
Then, and only then, invalidate Islam for ever. Expose the lie that is the Koran with the archaeological data (that Yemeni copy would do nicely). Teach them the vacuity of their faith. Leave them empty and defeated.
Then send missionaries to save them from their damned existence.
I think there are practical limits to what we can do in this war. Our own people would not accept bombing Mecca.
The first step is to educate our own people in the West that there IS a war.
As for totally destroying islam, I do not think it is reasonable. When religions are attacked, they sometimes get stronger and more fanatical.
Islam will be harmed more by drugs, sex, and rock’n’roll. Give them free HBO. Lady Gaga will do more than a fleet of B-2s.