I know this is a late comment and likely no longer necessary, but....
Marcus is quite right, an under discussed topic, for sure, and for the reasons he gives.
I would suggest that there is a commonality in all EMIS' that could be used as a core for any kind of development. Local authorities are concerned with issues of privacy, data retention and the like, so a shell app could be developed with these things in place. Everything else could become plugins and addons, --- hey, wait a moment, isn't that what Moodle does? A core with additional abilities that can be adapted to suit local conditions?
Good idea! Pity it seems that so few people have the willingness to pursue something like this.