Is it advisable to add an appendix section in a review paper? Background: There is an untapped aspect of a domain which I am currently writing a review paper in. The review paper is encompassing the domain in general.
I want to add a short one page proposal of that &quot;untapped aspect&quot; so as to carry forward future research. I plan to add this in the review.
Options

Should I just leave it out of the review and draft that as a separate paper with personal experimentation?
Should I add it as a appendix in our paper? (no experimentation).

Should I go for option 1 or 2?
Note: There is no page limit and appendixes are allowed in the journal.
If the paper has been refereed and the referee has not suggested adding an appendix, you should not do Option 2 (or at least you need to get a permission from the handling editor/referee). If the paper has not been refereed yet, you can do whatever you and your co-authors want. Option 1 (publishing a 1-page separate paper) is bad.