Shadowverse

1. For the first two weeks of the new expansion, we play using the old rules (rotation).

2. We vote for or against individual expansions and choose 4 that we will play together with the new expansion (rotation).

I would choose one or two expansions, no more.
Because, ideally, I don't see this tournament as Fragment described it – I wouldn't want to play with the tired meta that already exists or existed in ranked play 100% of the time.
As is known, in each new expansion, there are only a few playable cards in ranked play, mostly high-tier ones, so that players waste their currency, and all the others serve as fodder for the arena, while new mechanics and concepts are still attached to them; however, no one plays with them because of the too high power level of old and new expensive cards. Therefore, I think that limiting it to 1-2 expansions would force players to draw from the "trash pool" and allow them to reveal this aspect and create decks that are not too optimized but still thematic, using unpopular cards. The main problem here is that for some classes, some expansions are just unplayable garbage, but this will become clearer when we try to create a deck from them. In the worst case, each player could choose their own two expansions to balance this problem; there are many things that could be devised.

3. We only play with bronze and silver cards (unlimited).

Well, it might be a bit boring, but it might not be. In any case, there aren't that many cards in this tier, and only the most overpowered ones, so I personally want to try more cards of these tiers. And what I wrote in the second point implies this.

If we develop this topic – choosing the second point and a couple of expansions – it is necessary to limit legendaries, I think, because they are quite cancerous in silver. We can limit them to one or two cards out of three in a deck, or, as I think would be better, to one copy in the deck; in this case, all four (five? six?) types can be used. At the same time, this reduces the problem of poverty and the lack of complete sets of legendaries. I don't see such a problem with gold cards, although there are some cancerous ones there as well; in the worst case, we can allow two.
Well, these are all technical details that need to be thought out after we finally decide on the format.