This makes really no sense at all. First all, the PPCs you get nowadays are not really designed for mobile applications. 68K never was to begin with. They draw too much power, and computing performance is comparably poor.
Given the price point, this makes the whole idea unrealistic (or rather "what have you been smoking?" (-; ). If you want to go mobile, use a platform that is suitable for that. For small computing loads, ARM (yes, really), for complex computing, x64. I would believe running an emulator on a standard laptop is probably more power efficient than fitting a PPC into such a machine and run "something like AmigaOs" on it.