Exterior pockets are very handy. They're tempting targets for thieves. You' ll be tempted to carry lots of accessories. There are no great answers, but here are some suggestions . Bring your computer with you when shopping for a bag.
Some bags are too small, some too big, others too heavy.
Get an ergonomic shoulder strap. At some point, you're going to have to carrying this beast on your shoulder. Get an ugly bag. Or place your expensive computer bag into a lightweight bag, so it doesn't look as if you are carrying a computer. Get a bag on wheels.