So after some cross-checking I figured out one thing I did wrong with the Xbox build: no Dragonbones assets were included, hence my startup crash. So I added it back in and rewrote the bosses to where they were before, and this time I made absolutely sure that I included the required files so that the animations are processed as I originally intended. I also renamed at least two bosses based on their assets, and updated the boss rush yet again so that it's a sacred trial against the divine forms of the eight associate guardians. I also put together my first draft of the ice boss during the course of updating the boss rush, though I still have to nerf him for the initial encounter.
In the meantime the IARC came back for my original, discontinued concept which gave me some rather unanticipated yet still notable limitations: it turns out that the assigned ratings are only intended for use in IARC-compliant systems (so GameJolt, Steam etc. will still require me to do long form in order to include ESRB material). Needless to say, I had to reprogram my entire legal slideshow to accommodate this... and it required some serious work to properly detect user agent, platform and app root so the ratings are hidden from the sequence on non-compliant systems and services. (It also means that I won't be able to use a single package installer because it relies on the appx root which is used by the Universal Windows runtimes to differentiate between the Xbox and Windows versions of the game package.)
One final note in this update is that I have also finished writing the nerve agent scenario that leads into the mess involving the third guardian. (Obviously I was hesitant to do anything involving a biologic threat due to Covid19, but I ultimately decided to put that concern aside so long as I get it done right.)