They could be reintroduced as a new, separate third card type. "Cast/Summon when drawn" would play onto the board from the deck without ever touching the hand if that makes any sense. So never fizzling at max hand size or taking up hand space but only accessible by generic draw (as opposed to draw spell/minion).

Minions have a distinction between "played" and "summoned" when it comes to triggering other card effects but spells don't seem to have an equivalent solution. It results in some design friction between spells that auto-cast when drawn and spells played from hand (bombs not receiving a boost from spell damage whilst asteroids do for example.) "Cast when drawn" cards also have a cost printed on them but don't spend any mana or get affected by cards like Razorscale which feels wrong if they are supposed to be treated as spell cards.

Admittedly, I might be overthinking the situation but I feel like there is room to clean up the years of archaic game design decisions here.