It's a known fact. The Trans-Am is a GIANT homage to Char. What with turning a Suit RED, and making it run 3x better. The latter stated in the S1.
And I like how Katoma came out. His personality was a bit spot on with the original "Gundam WarZone" Katoma that utilized the STN-J. Eccentric, and quirky. I am a bit shocked you technically gave him the Win vs Trans-Am though, he would have normally lost versus Superior speed.
I also like your own tweaks to the STN-J (I don't mind either, it is meant to be a patchwork suit with a huge degree of flexibility to the design), although I saw that not all of them came into play, which seems to insinuate that you'll be returning the characters later on (I specifically note you didn't have him use the Shoulder Machine Cannons, Beam Tomahawk, or even the other =6= Heat Chains, and since you made him lose the Nu-Gundam right arm, if he does return that will end up being replaced, and I wonder just how you'll improve the STN-J (since you got good taste, if you plan to have him return I'll give you that freedom to what else 'new' is added to the STN-J's body. I really kept the AU to an absolute minimum so I think you'd be able to figure out what to use a lot better)
Honestly though, I was half expecting you to use Katoma's Re-GZ versus that Zno, but throwing STN-J only seemed Overkill haha. You completely surprised me with every turn and I congratulate you for that.