There is a disable tasker action so you could just use your own task to disable tasker.
An Event -> monitor stop could be useful in other situations as well, like tasker being killed by android. I have no idea if there enough warning when this occurs to run some actions but it could be something similar to Event -> Device shutdown.
There is a link for feature requests the tasker web page. I still find it strange there is no direct link to get to the tasker web page from the app , However I will just use Menu -> Info -> Guides to get there.