Having spent some time delving deep into the GSG-5"s inner workings I have some conclusions:
First, the GSG-5 is a VERY sturdily built weapon. The aluminum outer shell is quite robust and easily on par with the 10/22's upper receiver. Additionally, the bolt is located in a modular "inner" housing which creates a very strong combination which should be quite durable.
The plastic stock and foregrip tend to make the gun feel "cheap", but if those are replaced by sturdier pieces that do not flex or move, the GSG feels pretty solid. Does this mean the GSG can stand up to the "tire test" (being run over by a truck tire)? I don't know and I am not going to sacrifice mine to find out. I suspect the GSG will stand up to any test the AR-15/M-16 will and considering how long that rifle system has been in service something about it must be working right. What makes a rifle sucessful is not and never has been how effectively it holds up to deliberate destruction testing, or being utilized as a club, so for any purpose I would realistically put the GSG too...it will probably do well.
The GSG has weaknesses, but thankfully they are all easily corrected.
As delivered the GSG....
Bolt opens early
Sear fails to engage properly
Rear sight is ridiculous (GSG-522)
So far I have corrected all by modifying the hammer strut to prevent early bolt opening, modified the sear and sear housing spring to improve engagement and retention, and replaced the rear sight with a proper HK style aperture drum.
One last weakness of the GSG is the magazines...the base design in my opinion is VERY good and quite reliable, but the open slot allows external debris to enter and negatively impact feeding and reliability. The answer for this is to simply keep the mags in a fully closed pouch or container while carried and fabricate a sleeve enclosure to cover the magazine body when inserted, but this is probably at the ultimate end of the survival preparedness spectrum.