We had the same problem. Although using OJS roles will enhance the quality of publication, but having the comments of a larger group of individuals like the editorial board members is very useful. I think before this functionality becomes available in OJS, it is possible to release the issue as an online early (or early online!) without issue identifications (vol, num, pages) as the current issue. This way the public can view the issue contents and send feedback. If using this strategy it is necessary to describe the issue as this at the very top of the TOC. In particular you have to state that the issue contents may changes. The main problem with this is with harvesters, they are not intelligent enough to differentiate an online early issue, so they will harvest a premature issue because they recognize it as the current issue.