This question may belong to <Another site>, consider migrating - feature request
We all know how common it is for someone to ask a question better suited to one of the other SE sites. Some are more obvious than others and can be automatically detected. For example, any question with the latex tag is very likely better suited on https://tex.stackexchange.com/. When a user hits submit, he could be offered to post this on the other site instead. Very often users just aren't aware of these other sites, so a suggestion could do the trick.