it may be realistic, but highly useless in a game. lets just asume all weapons here are correctly made, if you want something like this implemented you could go on for ever.
for example in late war productions, many slave workers where put to use in the arms industrie of germany, as a result tanks like the Panther and Tiger broke down more often because workers damaged engine parts or maked sure that sprockets where too thin and broke off.
same with shells for guns ect, planes parts.
and besides, its a game, i dont want to get blown up half the time i want to take out a tank with a panzerfaust or another at weapon. it would get realy annoying.