@Prof.NightJack  
Unfortunately I don’t think there’s any fast Riders like Kabuto or Accel/Accel Trial. Although, the countdowns New Den-O does are pretty arrogant, even if normally accurate…
 
If you think about it, they each seek something though. Daiki just wants treasure, while the ‘treasure’ Trixie wants is admiration, and praise from others. They’re different, but similar in a weird way, the way I see it.
 
yeah, like I said, Tia as Shotaro busts up Tia + Luna as Double. …Luna and Cadence, perhaps? Tia as Accel? Shroud wanted the team to be CycloneAccel, not CycloneJoker… and in the end, CycloneJoker worked.

@Aurora Moon  
Dash as Kabuto only fits for the speed, other then that Souji doesn’t brag like Dash does.  
He simply stats how superior but in a very calm and factual, Dash likes to boast a lot.
 
Trixie as Diend… no, she’s after other thinking she is great and powerful, Kaito only care for the treasure, not what others think of him, he could care less.
 
Spike could be Ryuki or Kuuga from Decade, he fits both well.
 
Not so sure about Tia being Shotaro as Shotaro like to see himself as being “hard-boiled” but he has his doubts about things and he’s not good at hiding that, something it seem Tia can do, so he’s only “half-boiled”, but Luna as Philip works very well.

Yo, Fouzepone. If the mane 6, CMC, Princesses, Spike, Trixie, and maybe a few villains were Riders..who’d be who?
 
I’d concede Pinkie as Fourze, or OOOs. While Rarity’s personality doesn’t quite fit, her Element does give her a connection to Eiji, making OOO a possibility for her too. He merely takes it to a fault.
 
Rainbow Dash.. Kabuto, has to be. Hell, I can practically see this happen: “Heh, you think I’m cool already? I haven’t even BEGUN to show how cool I am! CAST OFF! CLOCK! UP!”
 
Trixie as Diend.. I can kinda see it, but she lacks Kaito’s love of treasure, and he’s a much bigger dick than her. Super Hero Taisen kinda proved that.
 
Spike… Ryuki? I don’t know much about Ryuki’s personality, but ability-wise, it fits. the Kuuga from Decade, perhaps, by personality.
 
Tia and Luna.. Double. Luna would be Philip, pretty easy, in a way. Philip’s still learning how to ‘be human’, in a way.. socially. Luna has to relearn social norms to fit in again. …Tia may not fit as well as Shotaro, however… so.. Hm. Slight issue there.
 
…Bah. x.x That’s as far as my brain’ll let me go for now.