I know that "He's not vintage" and all that crap. At the same time it allows for SOME part reuse from Krang's Android body. I know that it doesn't make sense given the size of vintage Krang and having a 12 foot Shredder... but at the same time it's a Shredder Mech suit driven by a villain crazier than Krang. He can easily be fit into the "vintage inspired new canon". Whether Krang is retconed into an Utrom in this continuity or not makes little difference. They can make a Kang the Conqueror homage with Ch'rell for all I care. All I want is an evil Utrom or Utrom-Looking Alien piloting a Giant Shredder Mechsuit.
I almost forgot that Multiversal crossovers are canon in most TMNT continuities. So no real explanation is needed for Ch'rell. Also, Ch'rell can be used as an excuse to refresh the Turtles with 2k3 variants. (New belts and using the existing figures with the modern heads and different accessories based on the 2k3 toys).
The Normal 2003 Shredder already has a semi robotic look that could lend itself for an Utrom android body. So in a way it makes sense to use Krang's Android body for him. The forearm Armor could be a piece that slips up the normal KAB forearms, the Lower legs would have to be new. The Torso would have to be new, but it could take some cues from the OG Android Body. Instead of the normal door, it could get 2 ibterchangeable chest plates. One solid colored and the other translucent.
The only reason I'm asking for the huge ass Ch'rell is because the theoretical KAB will be huge, since the upcoming Krang is not made to scale, just like the Vintage line. If we were to get a "to scale" KAB it would be closer to the smaller version released.
Because it a smaller Android Body is released, then a Mumm-Ra sized Ch'rell Android body wouldn't be as far-fetched. Whether big or small, a Ch'rell as Shredder would be badass.