this works, as long as noone renames the wifi card! :)

hardware/raspberrypi/wifi/files/default-wifi-powersave.conf

@@ -1,3 +0,0 @@
-# disable powersave
-[connection]
-wifi.powersave = 2

hardware/raspberrypi/wifi/files/interfaces-wlan0

@@ -0,0 +1,6 @@
+# SALTSTACK
+allow-hotplug wlan0
+iface wlan0 inet dhcp
+	wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
+    wireless-power off
+    

hardware/raspberrypi/wifi/files/wifi-powermanagement-off

@@ -1,12 +0,0 @@
-#!/bin/sh
-
-IWCONFIG=/sbin/iwconfig
-WLAN_IFACE=wlan0
-
-if [ ! -x $IWCONFIG ]; then
-    exit 1
-fi
-
-if [ "$IFACE" = $WLAN_IFACE ]; then
-    $IWCONFIG $IFACE power off
-fi

hardware/raspberrypi/wifi/init.sls

@@ -1,22 +1,8 @@
 # disable wifi powermanagement
 
-nm-conf_d:
-  file.directory:
-    - name: /etc/NetworkManager/conf.d
-
-nm-conf_powersave-off:
+ifup-wlan0-powersave-off:
   file.managed:
-    - name: /etc/NetworkManager/conf.d/default-wifi-powersave.conf
-    - source:
-      - salt://hardware/raspberrypi/wifi/files/default-wifi-powersave.conf
-    - require:
-      - file: /etc/NetworkManager/conf.d
-      
-if-up_powersave-off:
-  file.managed:
-    - name: /etc/network/if-up.d/wifi-powermanagement-off
-    - mode: 0755
-    - source:
-      - salt://hardware/raspberrypi/wifi/files/wifi-powermanagement-off
-      
+    - name: /etc/network/interfaces.d/wlan0
+    - source: 
+      - salt://hardware/raspberrypi/wifi/files/interfaces-wlan0