I have to imagine that the sheer volume of ID requests that would ensue on iNaturalist would make a Forum approach pretty unworkable here.
But maybe if there was a way for an iNat observer to “flag” their own (and others’ ?) observations into a pool of “ID Help Requested” observations, allowing maybe 5 such flags per user to be active at any time (kind of like “votes” on this forum), and having that flag be a filter option in Identify and Explore – then potential identifiers could specifically filter for those observations (along with all the other usual filter options) that users considered to be their highest-priority in need of ID help.