Add a countdown timer, or some way of delaying the detonation, so you can activate it then decouple. Would also need to function on an inactive vessel.

Suggested by Blinkin: http://forum.kerbalspaceprogram.com/showthread.php/25830-PLUGIN-0-19-1-TAC-Self-Destruct?p=322109&viewfull=1#post322109

Done.