Changed wording slightly (you now may include zerocost cards of any element without nonsensically having to produce quanta for that element).
The intent is mostly to prevent people from putting in cards just for the sake of fulfilling the 8 pawns requirement. Amongst pawns there is only rustler, parasite and chrysaora that abilitycost would matter in, only for para there would be a reason to not just put a photon instead if you dont use the ability anyway (or if you are already using 6 photons I guess). Therefore I see no need to restrict that. The wording atm also strongly implies that only the element the card is actually part of matters.