May be you're right about IGS... I don't have any Blu-ray titles nor I follow what are the latest implementations of menus. Since BD-J is not supported in AVCHD I gave up on java menus earlier this year and I was hoping you got that figured out somehow
IG streams are not encrypted - just RLE encoded like PGS. The problem is that there is no muxer to mux IGS with H264+AC3.