The following are just my predictions for the match-ups for the Dresssrosa Arc. Well, I don't think that all of these match-ups would even have 50% chances of happening. After all, I just made this up at a whim.
Monkey D. Luffy vs Donquixote Doflamingo - Of course, these battle between the captain would undeniably be a positive. I'm not sure whether or not Law will be fighting alongside Luffy (if ever he can still fight after his prevailing battle with Dofla in Green Bit) or he will be fighting someone else. It may be one one of the top four seats that represents the four suits of cards. There may also be a possibility of someone occupying the Heart seat (it has been said to be vacant in meantime) which may be a contender against Law. Anyways, the fight between Dofla and Luffy would too much hardcore as both uses Conqueror's Haki - it'll be a fight of battle spirit!
Roronoa Zorro vs Unnamed Spade seat officer -As the motif of Dofla's subordinates lies within the card suits, I've tried to translate Spade into Spanish and it turned out to be "Espada", which I believe is a term for "sword or blade". This name likely suggests that he is a swordsman of some sort, justS like Roronoa. Just a hunch!
'Sanji vs 'Trebole - As Sanji wishes to save Violet-chan from her servitude under the Donquixote Pirates, specifically under the Trebol Army, these two would likely battle for her.
Brook and Kinemon vs 'Diamante -' Due to the fact that Kinemon would likely have greater participation this time in his mission to save his friend, unlike what happened in Punk Hazard in his quest to save his son, Mononosuke. I just want to Brook to tag along with him. We had seen Brook and Kinemon to fight together fairly well despite their opposing fighting styles, the former that pierces with ice and the latter that cuts with flames - the irony!
I think the rest would be like this:
Nico Robin vs Jora
Nami vs Baby 5
Usopp vs Buffalo
Chopper vs 'Lao G'
Franky vs Machvise.
I would also like to have the rest of the Heart Pirates to rendezvous with the team and join the party as well:
Jean Bart vs Senor Pink
Bepo vs Dellinger