With enough time and effort, anything is possible.
No, no one has done it yet with the oem kicker sub. That takes high level inputs from the oem amp under the trunk floor, adds another amp, I believe, and then goes into the box. There's really almost no info even been posted about the kicker setup though, so you'd be in new waters.
Integrity concepts was the go-to box place that vanished, and the box I currently run.
Found this very similar model a few years ago, but don't know anyone that's used it, so I can't speak on fit or quality.
https://shop.wickedcas.com/scion-fr-...gic-box--.html
The $350 price is very fair for a custom fit fiberglass box. I just don't know anything about it other than what's on the website