Hmm... guess I'll focus on one field at a time. First up.
(Ability)Pokemon with dry skin lose an extra 1/16 health per turn
(Move) increase the chance of burn by moves is increased by 1.5 (so lava plume and scald go up to 45% chance to burn, for ex.)
(Move) WoW increases to 100% base acc.
(Field Reaction) Every 5 fire/ground attacks stirs up the volcanic activity and lava deals 25% damage to pokemon that aren't fire, rock, steel, or ground type. Ice types take 50%. Every water, ice, and flying attack used cools and stabilizes the area. (IE, it negates a fire/ground move in regards to the volcanic activation) Explosion and Self Destruct activate this field effect after the beginning of the next turn (ie, after any fainted pokemon are swapped out).
(General) Rock type moves get a boost to accuracy and gain 15% chance to burn. The rocks in there are hot, after all.
I feel like pokemon such as Camerupt, Magcargo, Magmortar, and maybe Torkoal should be OP in this kind of environment because of their... biology. But not sure how to boost 'em specifically.
(Move) Lava Plume's base power is increased. To at least like 100. Eruption's bp degrades with health at half the rate. Earth Power increased to 100 bp.
Incinerate now renders any held item held by the target unusable for the duration of the battle.