Using %VARIABLE% in commands

Hello,
working with some trackers there is the need to send commands over GPRS, maybe because of a Notification or specific Job.
when the GPRS protocol need to insert the IMEI in the command string to be sent to the tracker this will create a problem because the IMEI change from tracker to tracker requiring to create specific command.
It will be nice to have the possibility to use variables like in the notification, for example %UNIQUE ID%  or %CUSTOM FIELD%, to insert into the command string.
As an example: CS*YYYY*LEN*UPLOAD,time interval

where YYYY is the device unique id

thanks