If I'm following you, you mean you have multiple usb devices that when plugged in all show up as the same /dev/sda1 device, right?
I don't think it's possible to have multiple fstab entries for the same device entry. I tried that once and only got errors. But if your system is using udev, then it should be pretty easy to set it up to detect the individual devices when they are plugged in and create different device aliases for each one. That is, you can have a /dev/harddrive, a /dev/camera, /dev/flashdrive and so on. Then you can create different fstab entries for each of those devices.
Look here for info on creating udev device rules: