Windshield wipers and real grab irons are the only detail additions that I could think of. MTH has been painting rubber grommets around windows for several years, and I would assume that, on the new release, anywhere there was a prototype rubber grommet, it will be black.
The prototype photo of the museum LWT12 shows additional nose grab irons that were exclusively Rock Island and not on the original versions of Aerotrain that ran on other railroads.