WRT Skyfire's FSN/Bleach - I think you could just use the above scene as the pre-titles teaser, then wrtie a fic about Shirou interacting with the Bleach cast and getting himself to a power level sufficient to support bankai, or in this case multiple bankai. That's quite a way to go from thrid-rate first generation magus with a handful of low-quality magic circuits, after all - a big part of Saber's problems in canon were becasue he couldn't supply her with the energy needed to fight properly, but here he is, unleashing (fairly literally) the wrath of the gods of death... Possibly of literal gods given how many of the zanpukato are named after various kami from mythology.
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"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows
--
"Anko, what you do in your free time is your own choice. Use it wisely. And if you do not use it wisely, make sure you thoroughly enjoy whatever unwise thing you are doing." - HymnOfRagnorok as Orochimaru at SpaceBattles
woot Med. Eng., verb, 1st & 3rd pers. prsnt. sg. know, knows