Generally just use your regular off-line draft-saving tools (e.g., gedit, vim, etc.). However, in my opinion it is perfectly fine to publish your speculation with a caveat, e.g., "I believe this will work, but I am still in the process of testing it".
This makes sense to me particularly when there are not current solutions that look viable.
You run the risk of being down-voted, but if done in good faith, you will probably get enough counteracting up-votes to end up with positive reputation anyway.