Removing drive for offsight storage

[jerbo]

We have TS-5044D acting as a server and it works great.

We needed to set up a backup system that would allow us take two physical backup drives offsight (I will keep one in my car and one at my house and rotate them daily).

To accomplish this we recently bought a TS-XEL r5, configured it for JBOD and set 3rd party backup software (AllwaySync) to copy the entire contents of our server to all 4 drives of the TS-XEL.

The problem with the plan is that there does not seem to be a way to remove and install a single drive without losing the data.
It never occurred to us that ANY drive swap would require a reformat of the drive.
We aren't trying to swap drive positions.

We just want to be able to:
power down
remove a drive
power up without that drive in the system
power down again (the next day)
replace that same physical drive
Power up without losing the data on that drive.

Why is this not possible?

Or if it is possible please let me know the correct procedure.