Adding these would be problem for people who don’t have enough monsters, plus the fact that these conditions may result in player’s setup not working(meaning they’d be need to conveyed the condition before they hit the PvP button, where you again run into the first problem)
I’m all for alternative PvP rules, I think the best approach to this would be making arena based on a theme that changes each season, so that players know what to expect even if they don’t know exactly what they’re gonna get.
Two examples of the themes and possible arenas you could find:
Theme: Space-Time Arena
constant Gravity Field
constant Time Freeze
the in-game clock progresses faster/slower (making time-restriction skills easier/harder to activate)
all monsters entering the field gain the Weathering passive
Theme: Metallic Arena
boosts Robotic type monsters
boosts damage from Storm monsters
Poison damage and duration is halved
Earth type monsters gain Shield Entrance
Alternatively, they could make the same arena for everybody, but every 150sec (or so) one of the seasonal events happens and the battlefield changes, switching between modifiers analogous to the ones you proposed.
E.g. you start a match in the Space-Time Arena and all monsters enter the field with Weathering. 150sec after, the effect is replaced by Gravity Field, and 150sec after another effect takes place.