For me it is a robotic IC2 horse that runs on EU or nano/quantium horse armor of course.
Other then that It looks like 1.6 will be another nightmare of a patch for mod makers due to swapping to a whole new java and openGL environment. Let alone the new luncher that from what I've seen in a few mod author's twitter posts may prove very problematic to some modders but time will tell.
Err.. they are just dropping support for very old java versions if I recall correctly. Nobody was programming in Java 5 anyway anymore. OpenGL changes should only concern those modders who changed the engine (like the shader mods). The launcher change shouldn't affect any mod.
So all in all I don't think the points you mentioned will break any mods.