As an editorial board member for a low impact journal, I've been approached to provide comments on whether I think a proposal for a special issue is acceptable or not. I'm quite inexperienced in this role, and it seems rather different from reviewing a paper or grant proposal. I have been provided a list of guest editors as well as a justification statement, however, the special issue is not directly in my field so I can only assume credibility from prior publications (if I can find them).
Have any others been in this situation, and if so, by what criteria did they make a decision on acceptability?