Eating to regenerate, using lava, potions and blocking away to regenerate are definitely part of pvp in minecraft. But I get what you mean, sometimes I also wish to have some kits without all the fancy stuff, especially the speed effect and fire aspect.
I'd like to have an op kit with only the sword and armor and disabled hunger that takes at least 2 minutes to fight. A normal kit like the iron warrior without the golden apple should have at leaft prot 1 on the armor, maybe even more, so fights don't only last 15 seconds. At some point the results get too random and the time actually spent playing it too short compared to the time waiting for a match to start, like with the normal eggwars kit.
I like duels, but I think FFA and even more so OP FFA are terrible on cubecraft. You can't go around fighting people, since most players are in teams, and if you attack someone that doesn't want to fight you they can run infinitely since there is no hunger. Then if you get into a fight with someone that doesn't run away, the fght takes so long that there is a very high chance that someone else walks by and attacks you. And even if nobody does, without food it takes minutes to regenerate after a fight if the winner left with maybe 1 heart left, while in duels you can start another one straight away. Also if someone uses the /shop in FFA it breaks the game completely.