Y'know, it occurs to me to wonder if Gryphon and company could cadge a jet-model Striker unit into a back-mounted configuration? Obviously it would take some doing - particularly since the Miyafuji engine seems to require significant skin to surface contact - but it shouldn't be that hard, should it?

If that's not really feasible for story purposes, maybe they could incorporate SOME of the Striker's features into revamping the jetpack he just liberated. It already needs a good once-over, after all, so why not improve it while they're at it?

(This is of course assuming that Gryph's particular brand of mojo could even make the engine work, which... considering Mio's retraining, seems to be at least on the near side of possible.)