There has been precedence in other card games (for example Pokmon TCG Sun and Moon commons in the Evolutions set 2016)
But they will have only one special and one normal summon per turn
For example, if you have 3 Dark Magicians in your Main Deck, you cant put any more Dark Magicians in your Side Deck
If the Defending Pokmon has an Energy on it while Espeon doesnt, Espeon is still dragged Active and takes 60 damage
However, there are some advantages that being mindful of switching decks provides: Covering for weaknesses Introducing uncertainty in what deck you bring Being able to change your deck at any point improves the viability of decks or builds that have more skewed matchup spreads
A completely vicious evil looking clown whose "jester hat" tassels are actually eyestalks from the look of it, ending in almost Cephalopod-like eyeballs, which still gives the impression of jingly bells