Just because there may be a faster way to do it does not mean you should do it. One commented mentioned the entire system being down for the entire duration of the upgrade. That would be a no-go as far as the customer is concerned. One pump is a manageable inconvenience, half is inconceivable, all is grounds for termination. Gas stations sell more than gas, and those pumps draw people into the stores attached.
Let's say you can get the process down to five minutes somehow, and the customer is actually on board with this. You do have the risk of bricking an entire station at once now. Stuff happens when upgrading firmware. Five minutes turns to thirty. Good uploads get interrupted. Shit happens.
Lastly, why would you want to reduce your hours of billable time? You figure out a way to make your job part time and it will become part time, or part of someone else's job. Had it happen once. Literally worked myself out of a job.