I previously suggested leaving the back end of the bike alone and putting a mountain crank up front. It would be great for touring, but probably limited for regular riding.
That is probably the smartest approach at this point and can probably work out well. Personally I would have never bought the bike with 10 speed as a touring bike now. Down the road when/if 10 speed becomes mainstream for MTB and touring that may change. I think that both Cannondale and Jamis are off their rockers WRT how they spec'ed their higher end tourers.
The OEM gearing may work OK in the Cascades and Rockies, but I wouldn't want it in the Ozarks and Appalachians. Then again there are a limited number of really steep climbs on a route like the TA and they are short enough that they could be walked if need be. Depending on your route this may not be a big problem. What route are you riding? Also are you riding E-W or W-E? If on the TA and W-E I would just start out with what you have and see how it goes. You will have plenty of time to evaluate before you get to the Ozarks and Appalachians. Swap the crank out in Kentucky if you think you need it. If you need it in the Cascades and Rockies you probably need a more drastic change than just a crank.
An MTB crank with a 22t inner ring can be found for a decent price and if you want the old ratios back after the tour, just swap it back to the OEM one when you are back home.