They should have implemented battle pack concept in Duel Carnival instead. Each side had different pool of cards, and players duel with those side's cards. If we picked Resonator side, we only get to play specific Resonators cards.
The purpose of every PVP event is to promote the box sales. Fiend theme on the 1st day is basically to promote Infernities, but Konami don't care if people run ranked meta deck instead. Many people will make a purchase if they keep losing the match, that's exactly what Konami want.
they did something like that last year, but it wasn't a pvp event, it was to unlock Tristan; It was so cool you could test some decks like: inzektor, magnets, darklords, amazoness, blue eyes, gem knights and many others