I feel like you could still have Daimon as Yellow. You could write that, hey, the Anti-Hazard Suit helps ease his condition while transformed, or even make Go Yellow a drone he controls from Bay Area 55. I dunno, but you could do something! A problem is that Shibata has difficulty speaking, so I don't know if he'd be up for doing the voice-overs.
I just think replacements -- especially if it's something like one of their kids -- would be a cheap letdown.
It would be nice if Toei had the courage to do a reunion special for a team older than ten years, though. And a special that they have the courage to not piggyback on a newer show for. (Which I guess only Rider's been bad about.)
I'm not a Hurricaneger fan, but I thought only their 10 Years After was...well, I don't want to say "good." But it felt like a new Hurricaneger episode, it felt like a catching-you-up with the heroes, it felt like it was born out of love and interest and not just 'cause they could do it, which is how Dekaranger and (especially) Go-ongers's felt.
All five took part in that variety show that covered Shibata's journey last year. Despite the depressing reason why they were together, it was more heartfelt than anything Toei would write for a new movie.