It is possible to do this.There are two options:
The first is to provide a template project for users to add their music to an event, giving instructions on not to move markers, etc from the music event template. This does run the risk of users not reading the instructions carefully enough and causing some issues, but otherwise is the simplest solution. You can find information on how to support user-generated content here:
The second option is to have the music event use a programmer instrument, then have a custom system set up for the user to provide their music file(s) directly to the game. This is way guarantees the markers won’t be moved, but does require a little bit more setup. For more information on how to use programmer instruments, please check out the programmer_sound example in the FMOD Studio API installation examples, and read more here:
https://www.fmod.com/resources/documentation-unity?version=2.02&page=examples-programmer-sounds.html