Why would you want such a horrible feature? If this was implemented properly, Altium wouldn't be able to sell nearly as many licenses!
But seriously, if anyone knows, this would be great. We're constantly running into this problem at work - someone finishes up with Altium, closes it and walks across the building to do something else while the seat is still tied up for a few hours. We have five seats between eight EEs and we're a consulting outfit, so this can cause serious problems sometimes.