I've requested something similar in the past - I want to be able to define whether start dates, due dates and contexts are inherited from parent, from nearest sibling or default to a value such as "today". However, it sounds like what you're looking for is more advanced than that request - something like scripting to allow customization of the way it parses input. I can imagine this being quite hard to implement, though it's an interesting idea.
Stéphane