The closest I’ve come is combining two settings. I do this on two devices, one running Android 4.4.4 (KitKat) and another running Android 5.0.2 (Lollipop).
- System Settings → Wi-Fi → Advanced → Keep Wi-Fi on during sleep → Only when plugged in
- Play Store → Settings → Auto-update apps → Auto-update apps over Wi-Fi only
It seems to pick up updates at least a little more often when it’s plugged in. It’s not perfect, but it’s not a bad half-solution, and it doesn’t require Tasker or rooting.