At that point why wouldn't you get a Mac desktop to put somewhere else in your house, with (I assume) a better price for the performance and better cooling?
Then, I like the idea of tapping into a MBP or Mini for the extra power when you need it like coding.
For the Mac Mini idea specifically, I'd go as far as lugging it around with me in my backpack if it had more juice than a MBP and a battery.