OK, Problem solved.

the only thing what - at least for now...- seems to work is to make those changes directly in the userPrefs.mel


FROM:

optionVar
-sv "workingUnitAngular" "deg"
-sv "workingUnitAngularDefault" "deg"
-sv "workingUnitLinear" "cm"
-sv "workingUnitLinearDefault" "cm"
-sv "workingUnitTime" "film"
-sv "workingUnitTimeDefault" "film"



TO:

optionVar
-sv "workingUnitAngularDefault" "deg"
-sv "workingUnitLinear" "m"
-sv "workingUnitLinearDefault" "m"
-sv "workingUnitTime" "pal"
-sv "workingUnitTimeDefault" "pal"


even after restart maya kept changes. fingers crossed...