I'd like to see Shinji back just because it'd force them to write an explanation regarding his presence in these crossovers...
That's insanely optimistic of you.
What the hell is Narutaki? We still don't know. Why are BLACK and BLACK RX able to appear together so many times? We can only assume based on what we've seen before (in Decade and the RX movie), but nothing guarantees it's the same thing.
Many more unexplained things too.
As far as I know
Kuuga doesn't exactly hate Kamen Rider or Tokusatsu. He just doesn't care. I guess he can come back if Kuuga's producer is involved. If any character from Kuuga is to show up in these movies, I think it would be Kaoru Ichijou.
(hence why Kengo was the Fourze representative in last year's Movie Wars ... but Kengo wouldn't do for a movie like this as he is not a Rider.)
Ichijo would be an absolute thrill.
It's funny, but non-Rider characters would be more exciting to see back than Riders... kinda. Because we've seen so little of that in recent years... and because I want another Tachibana Tobei or Tani Genjiro. Ichijo would have been so perfect for that.
It may not be long before Gaku Sano will be too hard to get back either but Kouta's supposed to be some divine fruit god too almighty to return to earth, and there's enough Riders in the show that one of them is likely to be available.
We'll see what Full Throttle has to say.
Hibiki also did @Tokusatsuhero twitter. Most of other Riders from TV-Series came back in Decade (as did Kirameki, though as AU Agito).
He is in a similar boat as Kuuga. It seems he will only come back if the production team that got kicked out mid-series is involved.
Kabuto is kinda big now. I guess that's why he didn't come back for anything. He did @Tokusatsuhero twitter, though. Gatack and Hoppers has reprised their roles multiple times and Drake isn't exactly stranger to the Toku, too. Caucasus was back for the recent BW game. Dunno about Sasword, Hercus or Ketaros.
The thing with Mizushima (Kabuto) is that he retired from acting... AFAIK. He made ONE comeback for the Kuroshitsuji movie, but it was a special occasion only, he's still supposed to be retired.
Den-O is fond of his role (he did @Tokusatsuhero twitter), but his agency won't let him do it again. I honestly don't get how these agencies work. If you don't want him to be associated with the children show, why let him do it in the first place? Do you believe once he's big, everyone would just forget about his Den-O role? That's just stupid. Everyone else from Den-O is pretty much avaliable.
Was he in the same agency when he was cast for Den-O?
Here are the most likely to return IMO, not counting those that were in this year's movie:
-V3
-Super-1
-J (what the hell happened this year? It was his 20th anniversary, which looks nice next to X-Rider's 40th, ZX's 30th and Faiz's 10th, and he was there for the Kyoryuger vs Go-Busters vs Dino Sentai movie).
-Agito
-Ryuki
-Blade. Might as well include all 4 of them.
-OOO