I just took a trip abroad for any well deserved vacation. I made use of a very old suit case. I became glad I did not have to buy a new one. The reason is I noticed that the majority of the new suit cases were very similar. The cases we are now utilized to seeing at the airport have extra compartment(s) in addition to the case itself. These additions usually have zips. They are only large enough to hold small things like documents, folders, toiletries or small bits of clothing.
I draw your attention to this because of the risk you've got with this type of case. It is easy for someone to open the zips and help themselves to your belongings by cutting in the material inside after which simply zipping it rear to hide the damage caused.
My suggestion is that any compartments that zip up and can be used to access to the main part of a suit case mustn't be used at all and are simply locked so they cannot be opened. Utilize a suit case lock or super glue it if you possibly could. Whatever you do make sure it cannot be opened without bring awareness of the suit case.
Another thing you could do if you have such a case is to look at the luggage to avoid any surprises. Regarding me I will carry on using my old case until go for longer useful. It is a lot harder to get into my old suit case without someone noticing it immediately. So just be a little careful and take this advice.