Hello Yoni and welcome to the forum!
You could apply a condition to the task in question so that it does not appear within the workspace for the given contract scenario you describe. Conditions can be based on workspace field values or the answer to custom questions the user must respond to when creating the workspace. This is the approach we have taken in our organization. Another option to consider is making all tasks optional and rely on your users business knowledge to recognize which tasks are required for a given scenario. You could indicate in the task description whether the task is required or optional to remind users.
Cheers
Ken