I'm agreeing with rootranger here. He's pretty much said what I would have. I'll elaborate on a few points he either didn't agree with me on or didn't say much on.
-max 5 of a card: Agree, for all the reasons rootranger said. That is the key reason I always voted for 6 copies in rounds 1 and 2. (that, and the fact that I have a trainer edition and other players potentially didn't is why I voted max copies and upgrades every time)
-should nymphs be restricted: I'm not sure that's the right choice to take, but rootranger does have a valid point in that luck (and length of time playing elements; I'll have about twice the nymphs that someone who's played half as long has, for instance) are the deciding factors in how many and what nymphs people have. One other possibility would be to limit the number of nymphs one can use in a round, or the number of decks that can contain nymphs. By setting a fairly low cap on nymphs, one could minimize the luck factor of nymphs while still allowing them to be used. Limiting the number of nymphs per round (or per deck) unfortunately also has the potential for cheating, as one could simply claim they never used any if they went undrawn/unplayed, and just had pillars or whatever in their place.
-should marks be restricted: Honestly, I don't really care. I've recorded nearly 18000 elements games, and I've had one game ever where marks determined the winner. (and that was against a double draw arena deck, and I'm pretty sure they had hacked anyway, because that player had so many gravity marks and no tourney/league wins) The only time it's mattered in this event for me so far was in my first game with Jen-I, where his earth marks meant he had one extra pillar per turn than he would have had otherwise. (but I would still have lost even had he owned zero earth marks, just a turn or two later)
-should cards included have to be playable: No, because it is surprisingly hard to define what is 'playable'. Is a lone reflective shield in monoair playable if I use fireflies? I'd vote yes; fireflies produce light quanta. What about a lone reflective shield in monotime with fate eggs? You -might- hatch a firefly, so you could claim it was playable, though I'd vote no in this case. What about a lone reflective shield in monodark? Well, you -might- use steal on a light pillar -if- your opponent uses them, or you -might- steal a boneyard, kill a creature, make a skeleton, and have your opponent rewind it into a firefly. A lone reflective shield in monoentropy? You -might- mutate one of your creatures into a mutant with steal, steal a solar shield, make light quanta, and play the reflective shield. There's parallel universe, mindgate, and a surprising other number of ways that you could play that reflective shield without any obvious sources of light quanta. Now, in some decks, there will be no way to create even the most unlikely of scenarios, but you could still always argue that your opponent -might- use discord, or -might- play a mutation on your creature and make a steal mutant, or -might- nightmare their own ray of light, which you then play and cast reflective shield off of, and so on.
-should elements used be revealed after a game? Yes. I will point to my 5th game with deuce in round 2 to demonstrate one reason why it should be even when everyone is being honest. Also, it is possible to cheat. For example, against 10 men, I used a darkness deck with a single chimera to use gravity and make it a duo, and a rustler in a time deck the next game. 10 men never knew what cards, or even what elements, I splashed in those two decks. What if in game 5, I decided that gravity was my best option, and I therefore decided to send in a deck with a guardian angel instead of that chimera? Being able to retroactively determine what element you'd previously used is not a good thing. If you have to reveal them after a game, you can still cheat, but to a lesser degree, because you'd only have the knowledge of what your opponent chose during that one game to base your cheating on, rather than on all the rounds in between that one and the round where you lie about what you used. I don't know of a way to prevent that form of cheating completely other than to either require monos in every match, or to allow any number of monos from 0 to 7 to be used, but revealing them afterwards minimizes it.
