You can already record timed midi messages. In the lyrics editor, start playback and tap on the midi learn button. Now press whatever button you want at whetever time. It will be recorded with the current playback timestamp.
Regarding the duration for network clients. This is a compromise I have deliberately chosen. The problem with trimmed songs is that the playback does not start at 0 and does end early. This is done to ensure that all the time coding you did still works. The network protocol does not transfer the trimming points and time coding on the client would no longer work if I would send the trimmed playback position. So the answer is: I can't do that.