Teffy has some good points,
1)there is a good reason to ensure that each account can be "unique". E.g. by what ultra rares it manages to acrue.
-Note though, that trading would not necessarily negate this. If a particular card is sufficiently rare, it will take much more work to find others who have the one you are looking for. In fact, trading would help keep rare cards rare since it would alleviate some of the need for farm decks.
Also, since a player is "trading" they get a new card, but they also loose one in the process. So if, for instance, nymphs can only trade for other nymphs, accounts should stay relatively unique. The number of nymphs they own would not change.
Lastly, this would promote more player to player interaction, since in order to trade for a card you need, you have to find someone that has one. More social interaction would be good in my opinion.
From my understanding of the game: There shall be decks which player X will NEVER build and the nymphs you own shall make your account unique, and the decks you can create. Then it´s harder to copy-paste decks.
[...] My goal is to have people actually creating their very own deck instead of everyone playing with the very same deck. That means that there is a price to pay: the chance that you will never get to have a specific card -ever- because it simply is too rare.[...]
The best way to keep a very rare card very rare is to make it so players have a very small chance to see it. If a card is extremely rare, then it will be very hard to find another player that has one, just as it is very hard to find one to begin with. Moreover, to get ahold of said card, you would need to offer something of equal value in exchange... another "very rare" card.
2)A player should not be able to change upgraded cards without penalty.
-I agree with this... I think a solution here would be to have a "trade tax" on upgraded cards (maybe a few hundred
). For that matter, a smaller tax could be put on unupped rares if those can be traded as well. This would help with point number 1 as well.
3) Last but not least
A question I still have is : "Why should we have trading? What would be the benefits for the community ?"
If trading were put in place, the probability for winning shards in arenas could be brought down and they could be set to relics for pvp matches. This would help make them become "rare" once again and would also be another solution to the farm deck problem. It would cut out using farm decks for shards but would do it in a manner that would not leave players screaming about not being able to get to try out cool cards.
If implemented well, the goal of trading would be to help players get a few cards they need to make a really awesome deck, in exchange for a few they have that just don't fit. Trading would allow a player to flesh out a deck strategy. As long as the frequency of rare cards in the total card pool is fairly even, this should avoid the problems of every player making one or two highly popular decks since the cards to compose them would also be in high demand, and thus difficult to trade for.
Lastly, trading rewards players for interacting with other players. It would give players a reason to join pvp and actually TALK to the other player and not just leave when they realize they haven't found a farm deck... and who knows, maybe those of us who click pvp to play against a human opponent will get to do so.