My idea is:
When a player clicks PvP (Duel), he comes to a page similar to the Arena page (with Stamina, Intellect,Dexterity). Here, the player can choose, how many HPs he wants, how many marks, cards twice, and maybe extra options like games with open hand, old background, whatever.
When the player clicks ok, he comes to the screen where he can type in the opponent´s name as the normally does . Both players then start with the changes they made, means more HP, more marks...
I think this can greatly improve the PvP experience of the community, in tournaments, leagues... but also in chat games.
To the open hands: if you make a tick here, your opponent can always see YOUR cards. This way we avoid, that you can secretly see your opponent´s cards.