Bidding is basically a choice between buying expensive veteran players and starting with a card disadvantage, or buying cheap newbies but having a card advantage, or anything in between.
By adding "illegal", teams show that they knowingly built an illegal deck, and can prevent a situation where they would be forced to take a double penalty (both discarding because of a loss and a card penalty) for not being able to build enough legal decks.
By allowing a sub to play a match because your player didn't have the cards, you're circumventing the entire Auction process. That is the whole point on bidding for players, you know right from the applications who has the rares and who doesn't.
If Time had the option they should have built a deck that dragonsdemesne could use, otherwise it's a penalty. My 2
