Honestly, that sounds a lot like the revisionists speak about WW2 and the holocaust. While I think it isn’t necessarily bad to play as a german soldier, since they were humans too, you have to be aware that if you create a game that tells a revisionist view (like denying that the holocaust happened), then you will be jailed in Germany as soon as you enter the country.
Also freedom of speech does not give you the right to everything, like to falsely tell historic events. You can be offending, that is your right, but you can’t be a denialist. Besides, it seems you don’t live in the US, so you cannot claim a right to the US freedom of speech.
Regarding Epic, freedom of speech does not give you the right to use Unreal Engine for whatever you please. Epic is a business, and they grants you a right to use their engine, which they can at any time cancel since it is their business and they wouldn’t want any damage happen to their business.
This is common sense and is the usual thing any business woul do.
Anyway, why don’t you just tell us your brave, controversial idea for your game, so we can discuss it here?