So basically, I got the idea from a best of 5 emvee episode where you said, "your team looks like my team all grown up".

So, you would do them all in anything goes, to disregard tiers, and the first game is made of teams where all pokemon have to have 2 more evolutions to go, Magnemite, ralts, starter babies, gabite, etc. So you battle with those teams, and then after that, you go to game 2. Game 2 is made of the team you used in game 1, but all the mons have evolved once. You can change the sets, they just have to be evolved. After that, is game 3, chose your mega carefully :].  Game three is all the mons in their final forms, again, sets can be changed, and double path’s like ralts can be either.
Strategy in teambuilding would be a balance of viabiblity amoung all three games, maybe don’t choose a great game 3 mon if its game 1 form sucks.

The only ban I can think of off of the top of my head is happiny, chansey would be too stroink, rhydon would also either be banned or really good.