With the sources that I've tried, tsRemux said that they are unsupported. Maybe with some sources it works, but then it remains the muxer problem. Any way we take it, IGS works against us.
It's not so offtopic, maybe we can figure something out. You have an excellent application, but it doesn't keep the original menu, this way you can keep the original menu too. Maybe, in the future, if you will have the occasion and the software necessary, you could develop a muxer for these kind of files too and include it in multiavchd.