...We can't just keep adding new elements. The more elements we add, the more complicated the game gets, and the longer it takes to work out issues between them. On top of that, it's horribly difficult to remove them if it turns out they suck, when most new ideas do. You'd think having new elements would be great, but we have to add -really- fun elements, not just cool ideas.

We actually have a lot more space for elements, it's just an issue with keeping the game sensible.