Just mounted a full Mtb crank on the cannondale, (44 *32 * 22) and kept the front Tiagra DR. I was expecting problems with gettin it to work properly due to the much small rings, but I was very pleasantly surprized. I set it up with about one pennys worth of space between the DR and the large chainring, made sure that it was properly aligned, and tightened everything down. To my delight it shifted cleanly from the get-go. Yea, it's not as quick as my motobecane, but it's more than acceptable. This is with the Tiagra Brifters btw. It was a bit picky about setting the limit screws to advoid dropping off when going to the granny ring, but nothing that a few minutes of tweaking couldn't solve.
Final tuning may include angling the tail in ever so slightly, or possibly using a very small spacer to spread the rear of the cage. Right now I can easily use 5 - 6 gears in the large chainring, the whole rear cluster in the middle ring, and the top 5 on the granny ring. I can live with it.
Conclusions: At least for me, a standard road FD will work with a MTB Crank and brifters, just needs a touch of attention to set up and tune. Hopefully this will help anybody who is thinking of changing cranks to better deal with hills and loaded bikes.
FWIW, I installed an LX crank, the Hollowtech II with the external bottom bracket and intergrated spindle. It was a piece of cake, just needed a 9 dollar tool from Nashbar (or the 15 dollar one from Park) to install it. Looks like there is NO Way for there to be any creaking, squeeking or wear issues with it.
Who is doing the Bicycle Illinois this year, Cairo to Chicago for his fun ride.