It'll be interesting to see just how many secondary Riders they put in the game. We already know Gatack is in, and there will certainly be more (Diend, for example, is practically a shoe-in). They have to leave something for the inevitable sequel, though. I'd like to see at least one secondary Rider from every series make it in (save for Kuuga, for obvious reasons). Also, whether or not the secondaries will be playable is in question, as well. I can see them taking a DW7 approach and having the secondaries only be playable outside of Story Mode, or something.
I'm pretty impressed with how many mooks they've managed to cram on-screen, as well. This will definitely be more musou-y than say, the Bleach musou-clone Sony released a while back.
It's also important to note that according to the site, the game is singleplayer-only, so no splitscreen co-op, which is a shame, but not a dealbreaker. The aforementioned Bleach game was singleplayer-only as well, and it was still decent enough.
Speaking of which, has there ever been a kamen rider game with their civilian form? Bringing this up because I was just playing power rangers movie game for snes, and it was pretty dope that you spent have the level untransformed.
There have been a few Showa-era games to have civilian forms (Kamen Rider for the SNES, Kamen Rider and Kamen Rider V3 for the PSX). None based on Heisei-era series, though.