It would be quite annoying...
If this attack could be chained continuously making the device reboot over and over. However simply disabling wifi when your not using it would effectively mitigate this. I'm not sure how often wifi direct would query for devices but I imagine that is somewhat implementation specific due to the concerns of battery life. Of course that doesn't help if you're actually using wifi.
Though I suppose the reason Google declines to fix it is because their own devices can just be updated to 5.0. And once again getting others to update the stack is hard due to the nature of the android beast.