I almost got into this for a cement company and started looking at fleet services and realized that there already are decent products out there so didn't go too far down the road for GPS tracking.
I thought of the air tags since they are so small but there have to be chinese knock offs for a dime a dozen. But if you have gps on your vehicles this probably isn't so necessary.
To make data recording easier you could set up a upc/qr code scanner and then just implement a simple record take out and return interface running a raspberry pi with a cheap 7" screen.
Similar to your setup,
I was doing something like this for students going into a class room in 2014. They scanned their ID cards that were chipped. The scanner I had for the demo was big clunky drill sized unit. I was in for about $150 US for the setup. The code was really basic on the raspberry PI side. The monitor was touch screen so that makes it even more simpler to use. This would help reduce the need to pull up a webpage and doing xyz since it's press button to check out, press button to check in. The rest you have nailed pretty much.
