Aaron,
Ask yourself are you truly pushing the limit with a bag project? Will this be your portfolio highlight? Will this bag be interesting enough to the consultancies that you speak of? Maybe you will realize you need more of a softgoods/hardgoods wearable, or something in between… I try to hit the gym three times a week and I usually drive. My work/play bag typically stays in the car trunk and I rarely change at the gym.
I would try to spend as little time as possible on sketching pretty stuff and get down to user research pros and cons. Things change dramatically when you start to prototype. Whats the height and weight of your user? A 6’5 guy needs a bigger shoe compartment than a 5’7 guy. An all day bag carrier will need a different shoulder strap than someone who doesn’t. Try to jump into some crude and effective mock-ups. Deconstruct some cheap ass goodwill bags for patterns and fits. Be mindful of accessories compartments. Bust out the good ole pink foam and sculpt your shapes for a more accurate size and shape. I am interested to see what you come up with. Have fun with it.