Stack Exchange generally resists requests to add to this list (ELU was already an exception for us). However, if there's data to support a request, we can ask for this.
The best way to approach a proposal to add to the migration list is to post a meta question for one specific site and include links to questions that either were or should have been migrated there. If we've only ever migrated a dozen questions to Site X they're going to tell us to do that manually, but if we're sending questions to certain sites on a fairly regular basis or in volume, that's different.
My gut feeling is that ELL could be a candidate, Stack Overflow isn't, and I don't know about Academia but I'm leaning against. Rather than any of us guessing, though, let's look at data.