This could be standard, an option for ranked play, or a separate league using the current map rotation, I suppose, but I'd love to see a "fog of war" option: if an opponent's character is out of LOS of all three of your characters, they're not visible to the player. Location, buffs, what cards they play... nothing. They'd still be affectable by AOE's (Inspiring Presence, cones, etc), just not visible to your opponent.
As someone who plays a ton of Firestorm and Volcano, I think this is a great idea! I'll move and hide. While you're looking for me I'll cast Firestorms, and when you're out of moves, or nearly out, I'll start dumping the Volcanos. Works for me!
Fog should hide the hands too. Should spectating be allowed? Maybe spectators can only see chars visible to an opponent. Fogged SP would be pretty cool too, though the AI would likely mess up badly (more than normal) if it doesn't cheat. Still, it would be cool having a char peek around a corner and suddenly see a dozen Storges waiting
A tweak I'd like to suggest adding to the idea is for attachments to be fogged too. If I'm not looking at lava on the floor (maybe it's hidden around a corner?), then I shouldn't know it's sitting there. You should definitely have hands fogged as well. I may know you spent a turn doing something, but I shouldn't probably know what it was unless I visibly caught you doing it. That would make things like laying traps and ambushes a lot more fun. I don't see how you could fog cards played without initially fogging the hands as well... unless there's some weird outlier to the rules like Obvious Manuver? Avarice makes some interesting points, though, for cards that usually only exist in games where you're typically allowed full knowledge of an enemy location. My gut tells me that this would be the sort of ruleset that would be great fun to add to SP (where the AI is frequently allowed to cheat a bit anyway), and not so much in MP without certain cards being banned completely from the map. Sounds like a lot of work.... but I wonder what the map creation tools would be like if we all had the power to individually ban certain cards from maps we invent on a case-by-case basis? That would be a really neat tool for creating interesting new game modes, FoW just being one of them. I don't imagine spectating this sort of mode being allowed in a MP setting, without some serious time delay built into it. It's just too easy to game the system if you wanted to cheat, otherwise.
I've thought of this too, but I don't know how well it would work in this format. If it does, I'd like to include invisibility and camouflage for sneak attacks. Surprise roll too, perhaps?
So new armor types, but granting hidden status rather than damage soak, perhaps? It seems like it would be fun to include new cards with the new ruleset, and just treat it as an expansion. you could include new stuff that lets your character listen for nearby enemies, cast spells like Wizard's Eye, or do any of that flashy stuff that blind swordsmen do, like stabbing people who are standing behind them without looking. Derp. I should probably stop getting excited about step 3 when We're only just discussing step 1. Suffice to say that FoW could come with a lot of extra potential.