Personally I think the power move to get themselves right would be to get the license to IMSA and then release a separate game focusing on IMSA and its tree of championships as LMU focuses on WEC and its tree. Not as a DLC but a full blown game that happens to share many assets with LMU.
I have no love for s397/MSG but I'd buy this physics model twice to get the full experience of both series and put some extra money in the devs pocket to work with.