The troops being mostly used in the game, even with the rework of some kingdoms, is pratically the same. I still think that having another way to play pvp could help:
In summary: For the period of one week/tournament some troops couldn’t be used on Ofense/Defense, it could be an extra mode for PVP, so people could just ignore this mode and play the regular “Maw versus Mab” battles.
There is also @Rasper 's great suggestion of enviromental elements to increase troop usage if there is a bonus for using certains troops.