Just don't do them.

Is it even Super Hero Taisen anymore? The last two felt like just another Rider movie that just happened to give you Super Sentai as dessert. :lolol
That is what they need to fix right there, figure out whether or not if they are even making something that covers all superheroes within the Toei Universe.

To be fair, the Heisei vs Showa one was actually called "Kamen Rider Taisen" rather than "Super Hero Taisen", it was just part of the same series as films. So while the Super Sentai element was shoehorned in, they weren't really getting the shaft so to speak.

But then GP for some reason went back to calling the actual film Super Hero Taisen.

But the real answer to the thread is: Do a Kikaider, Kikaider 01, Zubat and Inazuman team-up one.

Two things:

Either take the Springbreak Sentai/Rider crossover, expand upon it, and have that be the movie.

OR

Just have like a team of whatever riders or rangers you can get back and just focus on them.

Just do this:

On the Rider side you have: Ghost, Specter, and whoever the fuck is willing to come back.

On the Sentai side, just bring in Space Cowger or whatever the hell next year's team is, and bring in....I dunno, Daigo? Just do that.

Have at least the new Inzazuman in it, and maybe the new Kikaider (Gavan Type-G's first movies wasn't great, but the other Space Sheriff films last year I think saved people's interest).

Unless Kikaider REBOOT ever gets a sequel of some sort, he'd need to be a pretty prominent player in the story since his own film ends with him dying and no-one being skilled enough at the moment to repair him.

REBOOT had a lot of plot points it was obviously going to expand in future films but probably never will now :(

By making it interesting to watch.
Not only are they bad, they also tend to be boring.

Parts of me hopes for a Kamen Rider x Ultraman film for Spring 2016 since it's the 45th and 50th anniversary of both series and Bandai has the toy rights for both shows. However I doubt Tsuburaya Productions would want to work with Toei any time soon.

I say have a bit more past actor cameo's like if Gaim or Decade or even freaking ryuki comes along as a major part in the story or is just a way to motivate someone have their original show actors comeback. I wanna see the original guy who played ryotaro back because he was one funny guy! Bring back the original ryotaro dangit!

He doesn't want to come back though.