I've been thinking lately about possible changes to mechanics in PTCG and what kind of impact they could have on the game, and I think the one that would deserve discussion the most is what changes a side deck would have to the game. For those unfamiliar, in other TCGs, the Side Deck is up to 15 cards that are separate from your main deck that you can swap cards between after your rounds. IE after Round 1, you can switch 3 cards in your main deck for 3 cards from your side deck to help you in the matchup to give you an edge in your Round 2. Of course, you can'd have four copies of a card in your main deck and another four cards in your extra, both decks would collectively adhere to card totals. This is common in other TCGs, notably in YGO and MTG. I feel like it could be used quite well in PTCG, especially in the current metagame. For example, you could side a 1-1 ULP Electivire line juuuuust in case of going against a Metal deck matchup, or if the opponent is playing a very search-heavy deck, you could side an extra N or two, or other disruptive cards. It could also lead to some very interesting decks that could possibly switch from one type of deck to a completely different kind of deck by changing your core pokemon lines. I haven't yet had a chance to test this with friends or anything, but I feel like it would spice up the metagame now and in the future.