There is a lot more cleanup/modernization work that needs to go into installer.dll such as:

-rewrite functions with Registry class from au2.0
-reorganization of files/filenames
-combine functions that have overlapping functionality
-remove a lot of unnecessary code/arguments
-remove all of the FX 1.0 functionality that is no longer being used
-pass around args (such as javahome) instead of repeatedly looking them up in the registry
-removal of unnecessary functions such as GetVersionInfo
-removal of MSI tick progress update's, as we no longer display the MSI progress dialog
-removal of unused browser MSI features, and installer.dll that goes along with it
-removal of unused resources
-removal simplify of remaining AU functions (removing UpdateConf* files)
-removal of unused copyfile.cpp/copyfiles.h files