Upgrade? Nah, complete conversion over to a scanner tower. To make it even more interesting, limit the hand scanner to a very short distance (500m), requiring you to place scanner towers to interact with by connecting your hand scanner directly to it to give you more range. Also instead of having a increasing of range over time similar to the radar tower, had it so that if you provide more power, the more range you will gain on your scans.
The current scan limits you to three resource deposits, this is another area where having multiple towers will display more than three deposits at a time.
Another threats mention something about deposits that are currently occupied with miner still showing during scans. Maybe changing the color slightly of that deposits to indicate that it's occupied.