Diesel Management with Raspberry

our company assembled a raspberry with a board for manage diesel refueling in our construction site.
We attach some files of our board.
It is functional but I would like a "clean" installation of raspbian and "rewrite" the program with additional functionality and more professional looking. you find a folder with python files.
The scenario is very simple. The operator must authenticate his personal RFID Tag and the RFID Tag of the vehicle/machinery. After that can digit on touch screen the Km/odometer of vehicle. At last the system close the relay to let the operator to refuel vehicle. All the information are managed on SQL locally and (when connected to the internet) synced with our server
We have also a GPS+RTC (Adafruit Ultimate GPS Breakout) but still not implemented. I think to use it becase our diesel tank are mobile and not always connected over the internet so the date and time are wrong. The GPS position could be useful to sort the use of diesel also by area (construcion site).
Let me know what do you think and if you can help us.
Thanks,
Valter