After some analysis I have identified the following closed-source packages as those that would be affected by any ABI changes (i.e. they link directly to microb-engine libraries or talk to microb-engine in some other way)
nokia-maps-core (nokia maps core plugins and libs)
camel-as-provider-0 (provides Microsoft ActiveSync email support for modest I believe)
libssoautologin (single sign on stuff, not sure what for, likely something Nokia/Ovi)
adobe-flashplayer (Flash player plugin)
tablet-browser-default-plugin (default plugin for microb, not sure what this does exactly)
tablet-browser-mediaplayer-plugin (media player plugin for microb)