Thanks for the feedback.
We've considered this enhancement, but there were few use cases in which this might break, e.g. if a you want to plan your work within a sprint, you'd probably want to set start/end date manually, or in case you move the task to the backlog, you may want Clarizen Go to "nullify" those dates, and more.
Our approach to date wasn't for Clarizen Go to set the dates for the user, but let the user control them.
We may need to reconsider this approach based on feedback though.
Hope this makes sense.