Well, first off, IIRC, part of the Sakura Taisen universe's backstory is that World War One, as we knew it, did not happen - there was a demon invasion, instead, all across the world... Which was several years in the past by the time of the first game/anime, which is, IIRC, set in 1924. An OTLish version of WW2 seems unlikely given the political situation presented and implied by the games - the various Koubu-equipped units are clearly international projects, given how widely the origin stories of the different groups' members vary, and that the chief social driving forces behind the two primary axis powers simply aren't likely to exist; Reni's presence hints pretty strongly that there's nothing remotely equivalent to the Treaty of Versailles grinding down German society and economics to give the Nazis their shot, while Japan's apparent leadership in anti-spirit technology gives them leverage into whatever formal treaty structure exists, which'd work strongly to allay the kind of 'small fish in a big pond' feeling that drove things to the point of the Pacific War.
Anyway, my point regarding the timescale wasn't actually that 'no, that can't work, they'd be too old', since clean living, good karma, and the occasional Kohran Health Drink mayhem could, I think, reasonably keep at least most of the cast going to that point, so much as that they'll have grown into very different people from the ones we knew in their canon - Sakura won't be a stumbling ingenue, she'll be a beloved great-grandmother, with photos on her walls of the latest generation's high school graduations, or something along those lines.
Given the kinds of things the Hanagumi were formed to fight, you could just as easily say that they ended up tangling with a boss-type who could slow down time, and they finished the fight to discover it had taken decades rather than minutes, if you want to have easily-recognizable versions of that crew around as mentors - but my personal inclination would be to simply pick your favorite and have the 'core cast' remember Rule One in regards to their kindly tottering silver-haired homeroom teacher.
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"V, did you do something foolish?"
"Yes, and it was glorious."
Anyway, my point regarding the timescale wasn't actually that 'no, that can't work, they'd be too old', since clean living, good karma, and the occasional Kohran Health Drink mayhem could, I think, reasonably keep at least most of the cast going to that point, so much as that they'll have grown into very different people from the ones we knew in their canon - Sakura won't be a stumbling ingenue, she'll be a beloved great-grandmother, with photos on her walls of the latest generation's high school graduations, or something along those lines.
Given the kinds of things the Hanagumi were formed to fight, you could just as easily say that they ended up tangling with a boss-type who could slow down time, and they finished the fight to discover it had taken decades rather than minutes, if you want to have easily-recognizable versions of that crew around as mentors - but my personal inclination would be to simply pick your favorite and have the 'core cast' remember Rule One in regards to their kindly tottering silver-haired homeroom teacher.
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"V, did you do something foolish?"
"Yes, and it was glorious."