Does it possible to activate the unity mode with the vmrun command ?
No, vmrun does not provide that functionality. BTW it's... "Is it possible..." not "Does it possible..."! 
Since a Virtual Machine cannot enter Unity view until VMware Tools are loaded then technically it cannot startup directly in Unity view. It would be windowed until the user logs into the Desktop and VMware Tools are running.
If you wanted to write a script that always made sure the following options were set in the .vmx configuration file before starting the VM and do not use nogui with vmrun then it will switch to Unity onec logged in and VMware Tools are running. If you do not have a need for the Guest OS to validate a login and instead go right to the Desktop it will then switch to Unity as soon as VMware Tools are running.
gui.fullScreenAtPowerOn = "FALSE"
gui.lastPoweredViewMode = "unity"
gui.viewModeAtPowerOn = "unity"