The cost of adding a feature isn't just the time it takes to code it. The cost also includes the addition of an obstacle to future expansion. The trick is to pick the features that don't fight each other.
“I am the baby in the family, and I always will be. I am actually very happy to have that position. But I still get teased. I don't mind that.”
“Although this is a fictitious story the history is real. You don't want to re-write history but you certainly want to portray events and characters as realistically as you can.”