#1. Personally, I prefer a big screen and bigger keyboard on a laptop..there`s nothing worse than squinting at a tiddly 12" LCD, or having to type with two fingers because the ruddy keys are too close together to type naturally :pissed:
As for #2, having the ability to run off a battery would be nice, but I doubt the Amiga would last long, also you`d have to put in a small power adapter to give it the range of voltages it needs.
Space will probably dictate that you`ll have to use the old external brick PSU.