I have a 13000mah charger unit with 2.1A out for my Samsung phone etc. Quite neat design; why not just get one of these if you're going to be carrying so much stuff around anyway? Could use it as a bit of spare power for the 12" as well.
I don't understand how that helps: that just replaces the power supply. So now I have my laptop charging from the power brick over USB-C and I still need the dongle to attach the phone at the same time as I charge my laptop. (I am guessing you meant to charge the phone; but not only wasn't the premise--the laptop is the device that is going to need to charge, particularly when you are using the phone over USB--it doesn't come up often as the power block for the laptop is just a 29W USB-C charger, so when it doesn't make sense to charge the phone from the laptop as if the laptop were a battery pack I can plug it directly into the wall.)
Yep I meant to charge the phone; my thoughts were if you are going to be carrying extra stuff to charge the phone then might as well carry parts that extend overall battery life. (And I was thinking of away from wall usage scenarios.)