The Proposed Question Sandboxes aren't really working.
This is just a suggestion for how we might go about this.
- Create a special tag, work-in-progress, sandbox-question, sandbox, under-construction, anything that gets across the meaning.
- Questions with this tag cannot be answered.
- Instead of posting proposed questions to the sandbox, you post it to the main site as a separate question, with the special tag. When someone attempts to answer the question, a message is displayed saying that the question is on hold because it is not yet finalised.
- As in the sandbox, suggestions and issues are pointed out in the comments on that question.
- Since it is on the main site, suggested edits are enabled, so improving the question is easier.
- For the same reason, you get reputation as an incentive (?) although you can't upvote something twice (normally, once in sandbox and once on the main site, but here it's one question) so I doubt this will work. Doesn't matter that much.
- When the question is finished, the author removes the work-in-progress tag, the question is no longer "on hold", and answers can be posted - the contest begins at this point.