Knowing Canon Grease, Onyx will most likely be revealed to be a massive dork underneath the badass.

And now I get the feeling that he and Ruby are going to be shipped together. WELP!

I just saw a picture of Kamen Rider Build Evolt in DevianArt by Razo777 and it's cool you should add the form in you story.
This is from 1 of its comment:
NEW GALAXY (build driver and evol driver voice) [Insert noise] (Stand by mix of muscle Galaxy and Genius)
"Yeah" "Ciao"
Are you ready?
Henshin!
Cosmic world builder Build Evol (SUGEE! MAJI SUGEE!)

I just came up with a good idea for an original Rider. When you introduce Tyrian you should make him Kamen Rider Tyrian. The Henshin device would be similar to Kamen Rider Killbas, a scorpion device in the build driver and then he inserts a scorpion full bottle. It works perfectly since he’s a scorpion fanaus. You can figure out the design yourself if you consider this. Here’s the sound affect from the Build Driver. Tyrian Scorpion (turn leaver.) Are You Ready? Scorpion, Scorpion, Scorpion, Tyrian Scorpion.

(\)_(/)
('.') This is Bunny.
(")_(") Copy and paste Bunny into your profile to help him gain world domination!

Did you mean lunch time ROYALE , dude ?

hmm, not too shabby. though I do wonder if there will be Scrylapedes(centipede grim) a bit early in this. no doubt an Evo-grimm from that one will be quite the challenge. looking forward to more. until then, later!

Just saw Volume 7 premiere. Penny’s creator was introduced and he doesn’t look like the type for Metal Build, so if you do your take on the Grease movie then make the scientist from Grim Eclipse Metal Build. Also the idea of mass producing Penny is possible since she was restored after death Volume 3 death, making her perfect in becoming Phantom Crusher. Is Blood Stark going to manipulate the kingdoms in order to start a war between them in order to power up the Evol Trigger through the updated rider system like in Build?

To author
RWBY Volume 7 trailer just got released and it has some new Grimm in it, centipedes Grimm, and Saber-tooth cat Grimm. Those make some interesting EVO Grimm.

Just saw the Grease Movie and I now agree that evil Penny should be Phantom Crusher, and since there was a few Phantom Crushers, (almost like foot soldiers) then you should have a few extra evil Penny’s. I would probably give Metal Build’s role to someone else like the scientist from Grim Eclipse or Penny’s creator who probably have a desire for world domination (just a suggestion)

So I had a Idea for Metal Build in this story.

He’s like G4 a robotic soldier that Ironwoods men created to copy on the build technology and to combines with not only havens robot soldiers but the guardians as well but he’s gets taken over by a virus that forces metal build to go on a rampage wanting to fight Haven’s strongest so it’s up to grease to stop him.

This would take place sometime during or after volume 2 or later on if you want

To author
Is your Aion/Symphogear going to be divided into 5 arcs considering there are five seasons of Symphogear? And will Shiro and Kari be in it as well?

To author
That reminds me, what are the FullBottles that Sun has?

To author
True, but you do realize they are entering Tundra climate, also will the Batta/Bike Best Match Background music be Let's Go Rider Kick? And what James Reed mention in his comment about an evil version of Penny does sound interesting, but I don't think I'd have her be Kamen Rider Metal Build, but Phantom Crusher.

Is it possible for you to do a RWBY Chibi spin-off for Build a Legend?

An evil version of Penny can be Kamen Rider Metal Build if your thinking of doing your take in the Grease Movie.