The CNK tracks also have major restructuring layout wise in places for (their own words) "pacing and to make the gameplay more in line" so I'm not sure they would do CTTR 1:1 when it's more obviously different from CTR than CNK was.
From what I gathered from all the interviews with the devs the restructuring is mainly in play to replace the anti-grav sections from CNK with normal track to drive on. As from the CNK tracks showcased so far, comparing them back to the original CNK game the track layouts are pretty much spot on the same apart from the anti-grav sections. So yeah, I think you might be misguided on how much the CNK tracks actually changed, cause from what they showed so far the restructuring isn't actually that major, or at least not nearly on the same level of restructuring the cttr tracks would need.
Here are the two things that makes CNK tracks so fundamentally different from CTTR tracks:
- CNK was a kart racing game that tried to emulate CTR, with similar gameplay and boost mechanics, with tracks that were reminiscent of CTR track designs.
- CTTR was partly a combat/arcade racing game, with gameplay very different from from the other titles that focused heavily on fighting other karts over actual racing, with tracks that primarily accommodated all the fighting going on and had very little interesting layouts because the racing mechanics simply weren't refined enough to even accommodate tricky track design.
The CNK tracks simply fit the better CTR gameplay like a glove because they were already designed in that way, while the CTTR track layouts from themselves simply don't. If they bothered to make anti-grav work in this remake the CNK tracks would've still been a perfect fit without any need for restructuring. The CTTR tracks are just not fit for the CTR style, the amount of redesign they need to put in to make them remotely enjoyable in this game is simply incomparable to what they actually did to the CNK tracks.
edit: And don't get me wrong, I don't actually hate CTTR or anything. I enjoyed it for what it was. I just recognize that the tracks while fine for that game, just not add anything of value to CTR and unless retooled heavily will most likely consist of the worst tracks in this remake. It's not that hate having more content, but I played with enough people online that will consistently pick Nuke Town in a Call of Duty or Baby Park in a Mario Kart to know that having bad content in your game will absolutely diminish the overall game experience and that less is more sometimes.