When asking this question the question of what constitutes a related question came to mind, in particular for "flip-side" questions (e.g., "What is the argument for X?" and "What is the argument against X?"), though some questions marked as specific to a different denomination could likewise be related (e.g., "Why do Catholics reject X?" and "Why do Lutherans reject X?") even if they could not be merged into a single question (is question merging ever done on Stack Exchange?).
Of course, the "Related" sidebar is supposed to provide some of this function, and I could easily see difficulty with adding too many links. I wonder if allowing static (human-generated) related questions at the top of the list on the "Related" sidebar would be useful. (My guess would be that such had already been suggested as a feature request for SE and rejected for practical reasons, but it is remotely possible that I might be the first to suggest the possibility of such and that it is something useful and practical! However, I am skeptical enough that I would not present such as a feature request unless at least one or two others confirmed that it might be useful--practical is more for the SE people to decide, I think.)