Is it possible to add custom music to the game?

The option from message number 11 can actually be implemented if the map has its own installer that distributes everything to the correct folders. It's not difficult to create an installer like InstallShield Wizard; there used to be a function for compiling such installers built into some high-level programming language compilers (Borland Delphi, for example), and it could be done in a few clicks. I think there are still such tools available. Here's one of the first results from a Google search: https://jrsoftware.org/isdl.php#qsp Regarding the map size, the problem isn't the size itself, but the large number of objects and other elements, which increases the size of the save files and can corrupt saves during extended gameplay. However, music and various texture mods won't cause any problems, as this information won't be written into the save file.