Ok, so great news.
Thank you SO much to those of you who suggested using multiAVCHD. I’ve had a play around with the program, and was able to remux my blurays, replacing the video stream with Harmy’s original .h264 video, and the DTS audio tracks which Encore would not let me import.
What’s even better is that I’ve been able to add 32 subtitle tracks, and additional audio tracks as well. The menus will still only be able to link directly to 8 audio tracks (thanks for Encore’s limitations), but there will be more included on the disk, which I will index in a document to be released with the next version of the bluray set.
I am extremely grateful to the community for all the positive feedback and helpful advice. Version 2 of this set will be available as soon as possible, I’ll keep you updated.