Sounds like you're trying to increase the incoveniance of traveling with the MBP and decrease the iMac's In all honesty, I've exclusively used laptops for over 10 years (and prior to that a desktop, laptop setup) and to be honest. Its not that much trouble. If you are going to be mobile pack a second wireless mouse, you don't really need a mousepad with the current generation mice and its fairly easy to store the powercord.
The bottom line, you don't need to convince us that moving the iMac is a good idea, it seems like you've already made up your mind in that department. Its your computer and do what you think is best for your needs. I think a bunch of us offered our opinions and solutions, its up to you to find what works best for you.