Better scheduling, more rest before flight and less hours every week/month/year will help but till it happens some threat mitigation survival techniques need to be deviced. Fatigue should be included in briefing as a threat. Like many suggesting cabin crew periodic check, hot towel/ cold towel, more caffeine may be or when it's worse a Modafinil tablet. It's suggested to combat pilots so couldn't be a psychotropic substance. Better check it. I used it on a nine hours drive starting early morning and it did help. May be they knew all this but missed out. If not, good to start now.