You can use Start date/time: in the future to do that option.
I think it's good.
Your respondents will feel a bit taken for a ride if they read "Survey hasn't started" and you have invited them.
PS: good idea the new forum, but what for ideas.limesurvey.org ?
The aim is to drive more attention to ideas.limesurvey.org and link from here to the ideas and back from the ideas comment fields to threads here.
I think the discussions in one place is better. Perhaps the board software could mimic the ideas tracker features like voting in future. But the momentum is on the forum not on the comments on ideas.limesurvey.org