Theres great mana fixing to make decks better, and there are powerful cards that can be played in multiple formats
The last ability of Clive's Hideaway will allow you to cast both exiled cards without paying their mana costs (assuming you control four or more legendary creatures at that time.) In a Two-Headed Giant game, Traveling Chocobo's second ability does not affect triggered abilities of permanents your teammate controls
Brightspear Zealot's last ability will count any spells you've cast this turn, which may include Brightspear Zealot itself
6 Hypergenesis If youre looking for an easy way to help everyone cheat in a bunch of creatures, lands, artifacts, or enchantments, then Hypergenesis is the way to go
Humans you control gain haste until end of turn
Thus, we get a land that generates two white, a blue, and a green, with absolutely no drawback