Cascade is interesting and it means that me or dennis will have to dive in and see we can get things working (or not). It might be possible, then again, it might not be.
Setting the mana cost to 0 might work, Card.getSpellAbility[0].setManaCost("0"), you have to change the mana cost for the SpellAbility, Card.getManaCost() is just a throwback that the gui uses (I think). Non-targeted spells like
Wrath of God or creatures would be easier to do (because you could just add them to the stack) versus spells with targets but that isn't really a solution.