There were many files that were changed as the engine framework was updated drastically in that time period. I would have to contact the specific engineers that worked on these optimizations and comb through the changes to find out what files to revert.
Even still that would be a risky venture since reverting these files may impact the engine in a negative way. A suggestion one of my coworkers had is to create a 4.10 build and only pull in functionality that you need from later versions. Then migrate your project to this highly-customized 4.10 build.
Otherwise you may have to wait until we are able to put that functionality back in or use clever workarounds.