kernel is already optimized for device, it doesn't have to run anywhere else so all required functionality should be built in. wifi drivers aren't because of need to swap with injection drivers.

if your looking for fast booting, your best bet would be to replace the current init system with systemd or maybe upstart. however, with systemd, this would involve reworking all the current init scripts to become .service files to make the most of it.

question is, is it really worth it? device has long battery life compared to laptop. its usually not (re)booted very often as it needs to be always on.

edit: appaerently already uses upstart.