So, at this moment in time I can answer 2 of your 3 questions...
I'm really curious to see how you can bring a legacy element to an arena style game
In NEXUS you play the role of the Lanista. A kind of fight manager and promoter. One part Mickey Goldmill and 2 parts Don King.
Don King didn't care if Mike Tyson lived, died, won or lost as long as he makes some coin and we all remember his name.
When is this launching?
That's a secret for now.
just how "rude" is the humor?
Really Rude. Keep children AWAY from the NEXUS.
That being said I play a version of the game with my 8 year old son by replacing the cards and using Disney Infinity characters instead of our miniatures. The game is very adaptable and the rude humor is just for flavor. It isn't essential to the core mechanics of the game.