The FORM1 does not prove that the unit is operating correctly when installed in the particular aircraft. For example the antenna system could be operating well below spec and the signals are not actually reaching the unit, this can only be tested reliably using a calibrated test set. There can also be many problems with distorted and worn mounting trays - the single screw is often connected to a locking pawl which can fail to engage with its receptacle and even though the screw is tight, the unit is not actually secured. Connector pins can be worn/broken/pushed back and particular functions may also not work reliably even though the box appears to be powered up.
I would say that removing the unit and sending it away would not be a problem but the fitting and testing by an LAE is a must.
The aircraft should not be flown with the unit removed even if MEL authorised - the MEL only allows for the system to be unserviceable - not removed from the aircraft.