If you want to be efficient about your inventory, carry standard grade two locks such as those from LSDA, and others, that have key in knob cylinders you can exchange for other keyways, and then carry the popular cylinders seperately. Saves you stock space in your vehicle.

Just remember to carry the three or four stock finishes.
If you don't have the tools to rekey the lock, you definitely shouldn't be out drilling them in the first place.
As a general recommendation for drill bills, when required to drill, use the smallest you can get away with. Looks more professional that way.
And yes, it should be very rare that you actually have to drill a lock, and should NEVER be a first resort. This is where creative thinking comes in.
Take the time to properly and fully diagnose the lock problem issue and make sure there's actually something wrong with the lock before reaching for the rotary picking tool.