Yes I agree the most you can do is hide your luggage or, possibly put a chain and padlock through all the baggage handles.
On my rack I use a flexible cycle lock through the case handle and rack. Deterrent if nothing else.


1969 4/4
1995 plus 8
1996 Plus 4 4seater
2002 Aero S1
2013 M3W
2014 Plus 8