1. What will I miss if I choose to do this route apart from ice cream in Missoula and Yellowstone.
2. Would it be a big mistake to take this route because its not very pleasant for example? If the published route is ALOT nicer than this route then I'd rather do the extra 400miles and run the risk of not getting to the other coast, a pleasant journey is much more important than the final destination.
1. There was a lot of good stuff on the section you would be missing. I personally would not want to miss Yellowstone or the Tetons. I would also hate to miss Togwatee Pass We enjoyed lots of other places too.
2. I don't really know your proposed route so I won't speculate on how it compares.
I will say that 70 days isn't an unreasonable amount of time to finish. We took 73 and we started off real easy in the beginning since my companions had no opportunity to train before the tour and neither had been riding at all until just before the tour. They trained as they went and got in shape pretty quickly, but still it cost us at least a few days. I prefer to allow some extra time so as not to be against a deadline, but 70 days is very do-able.
Starting in Florence helps a bit.