Originally Posted by Brsis
The SS uniform isn't used in any official Hetalia art, with or without insignia.
Aside from the convention staff likely being uncomfortable with it, you are likely to get negative responses from other Hetalia fans. As a group en mass, we have a (partially deserved, due to the irresponsible actions of some) bad reputation, and many fans are now very aware of what is going to make them look even worse. You will inevitably find yourself on 'bad cosplay' websites, being chewed over on the Hetalia communities, and any pictures that get taken will follow you forever all over the internet with cruel comments attached to them because you are not the first person to have this idea and this is what always happens.
It's just kinda not cool.
If you really like the uniform and the history surrounding it, great! Find a WWII re-enactment society or some other legitimate venue, or else keep it for private occasions. If you want something you can wear to a general convention and just really like the styling and the look of it, why not look into a military styled anime series (Something like Dolls maybe) or OC it, switch out all the insignia and probably also the accent colours, but keep the cut and the lines that make it so smart looking. Or look into the hundreds of equally (In my eyes at least) smart and good looking uniforms which are less problematic to build a Hetalia cosplay on.
I agree with you 100% as someone who does WWII Re-Acting I'm with a German Luftwaffe United that is why I suggest either the Air force or the German navy they both have one offensive uniforms. If you want to Cosplay with a German Uniform then be smart about it.